SomeoneSomewhere:
Yeah, that's a problem. It doesn't really take any more staff to use a longer train - a second ticket collector would be good, but not really necessary.
To some degree the problem is probably predicting ridership in advance. That could explain the mostly-empty buses running around and the mix of over-crowded and empty-but-massive trains.
I think you'll find it does take more staff to use a longer train - this is the reason they're running shorter trains!
I'd rather have a packed train ride than no ride at all. I ride the J'ville line regularly and to be honest, compared to many routes we have it pretty good.
Though the fact they've cancelled several runs in the timetable is a niusance, it incentivises me to make sure I'm at the station on-time ;-)
It has caused me to drive my car in a few extra times when i've been running late and I don't want to wait a full 30 minutes for the next peak-time run.
If they ran hourly i'd be having a rage, so the bus routes that've dropped to this are frankly unacceptable.
I personally get travel-sick riding in buses so rarely do so, the train is at least a viable alternative (I have to drive to the train station, but still).