the only car i've ever sat in that had this feature is the kia carnival btw. 

I guess by ‘back row’ you’re talking about cars with three rows of seats? Otherwise you would probably have said ‘rear seats’.

If you mean third row, because they are often between the rear wheel arches, so there is only width for 2. If you mean 2nd row, the centre seat is often compromised by the floopan shape over a transmission tunnel; less of a problem in a lot of EVs.

I don't imagine he means third row.  Maybe they exist, but I haven't been in one that had two comfortable (for adults) third row seats - let alone three.  (Exception - "people carriers" - IOW small buses)

Front wheel drive cars don't have a "transmission" tunnel, nor do some SUV's and utes with sub-frame ladder chassis have much of one - maybe a bump 50mm or so high. 

Cars have got wider, but doors have got thicker with side protection beams and probably adding thick panels with moulded armrests etc to keep passengers further from harm in side impact safety tests, included being beaten to death by being too close to an exploding airbag.

I guess in the end it's a marketing decision, have two comfortable rear seats with a dicky seat in the middle, or three not so comfortable seats.

Or move to America, buy a Silverado, preferably in that order:

Batman:

 

Why do car manufacturers make back row seats that are comfortable only for 2 people.

 

Why can't they make 3 bucket type seats

 

It's form (style) over function isn't it.

 

/end

 

Assuming you are talking about the 2nd row, In short, they can. (Third row is typically between wheel arches, it takes either massive car (i.e. patrol Y62), or a van with the seating high above the wheel arches to fit three in full stop.

i.e. Peugeot 5008: 

two generations old kia carnival

So the question is why, if they can, why to car makers choose not to, and to do a 40/20/40 split instead?

Basically I think it boils down to the following:

• Many car's simply aren't wide enough to comfortably seat three adults across the back (especially given the outboard seating postions can't be too close to the doors for safety & side airbag clearance reasons), so they optimize the setup for two, while keeping the ability to seat three in a one off situation.
• As others have said, the center, 2nd row seating position is inherently compromised by things like the transmission tunnel (often primary for rigidity, not a driveshaft) , center console, front seat runners, overhead aid con ducts (i.e. toyota fortuner), that the experience is going to suck for an adult anyway.
• consumer demand for stuff like ski pass through's, fold down arm rests, shorter center headrest for driver rear visibility etc, further comprise the middle seating potion.
• A 60/40 fold-down split is reasonably practical, with matching seats, a 33/33/33 fold down would likley be needed (67/33 would kind of suck), adding build costs from a third locking mechanism.
• For most new car buyers in key markets (that are not shopping for a people mover, or passenger van), carrying more than 4 adult sized people at a time is a fairly rare use case. Even in the minivan space, many are moving to a pair of captains chairs, in place of the traditional three person bench in the 2nd row.

I think the last point is the biggest one. A 40/20/40 2nd row configuration is simply seen as more appealing to most new car buyers

Its a niche requirement. The number of times that people require 3 adults to sit comfortably in the back seats is very rare. For short, infrequent trips, people just suck it up. If you are one of the rare cases that needs this on a regular basis you buy a Kia Carnival or equivalent

Batman:

 

Why do car manufacturers make back row seats that are comfortable only for 2 people.

 

Why can't they make 3 bucket type seats

 

It's form (style) over function isn't it.

 

/end

 

My thirty year old Civic has four bucket seats... In the whole car.

nakedmolerat: The best and most comfortable van you can have - Toyota Alphard/Vellfire.

And it comes with the customary allowance of reversing into every carpark, no matter how many times it takes😀

nakedmolerat: The best and most comfortable van you can have - Toyota Alphard/Vellfire.

Those don't have the tipple bucket setup OP is looking for either. Typically they are two bucket chairs in the second row (but sometimes a normal 40/20/40 bench, and a 40/20/40 setup in the third row (with a crack dead center for the person riding in that seat).

Something like a Mercedes-Benz Valente, or a Ford Transit Tourneo does. (The latter gets a 30/30/40 setup in the front row too, which us unusual these days)

Senecio:

 

Its a niche requirement. The number of times that people require 3 adults to sit comfortably in the back seats is very rare. For short, infrequent trips, people just suck it up. If you are one of the rare cases that needs this on a regular basis you buy a Kia Carnival or equivalent

 

Pritty much. Regularly transporting four adult size people, let alone five is a pretty rare use case for private vehicles. (noting that if one needs to transport more than 6 or more adults size people, it pretty much requires a van of some sort).

One thing to remember is that automakers are catering primarily to new car buyer's tastes. Takes a pretty big car to seat three adults across the back of comfortable to start with. Means that such buyers are in a higher price bracket to start with. (i.e. Camry, Commodore, Highlander, CX-9 etc.). Once you are in that kind of price bracket (and size of vehicle to park), for somebody who is regularly traveling with 5 adults, the option of going for something like a Kia Carnaville, or Hyundai iMax, so everybody can sprawl in comfort over three rows is pritty tempting. Both purchase price, and fuel consumption are in the same ballpark.

Note that in europe / UK where fuel is more expensive, and parking spaces are smaller, there is a whole class of of small - medium people movers (either 5 or 7 seat) that offer tripple bucket seats in the 2nd row.

https://www.carwow.co.uk/best/cars-with-three-separate-rear-seats

Ignore the Q7, Model X & XC90 from that list. Yeah they have three individual seats, but the center ones are smaller than the outer ones.

Used car buyers are ultimatly lumped with what new car buyers cast off (plus what we can import used from japan). But the choices are slim in this space, and not much for people what don't want to pick up the running costs of a larger car or van. Peugeot 5008 is one choice, but some will be put off by the badge, and a cira 2006 carnival is another, but some will be put off by the v6 petrol running costs.

MadEngineer: They do. It’s called a bigger car.

yeah like how the BMW 7 series only has 2 at the back?

if your car is wide enough to fit an extra seat between the driver and front set passenger then you can have that.

so buy a Ford F150, Chevy Silverado, Hummer or Leyland P76. Otherwise get a TARDIS :)