A supported life of 2 -3 years from a phone does seem very short. My last phone cost ~$1,000.
I can't think of another situation where I would accept a service life of 2 - 3 years for something that expensive.
I would rather see manufacturers and retailers invest in firmware for longer than invest in tacky bloat-ware - 90% of which I'm going to disable the day I get my new phone.