Companies are incentivized in the long term to make good products. This incentive usually eclipses incentives that our (often justified) anti-corporate suspicions invent.
Smartphone usage must be pretty close to saturation point, in the developed world at least. Samsung, Apple etc release a new, expensive device every year, and it's natural that they are going to want existing customers to upgrade.
I think the only way Android users (of non-Google devices, that is) are going to get software upgrades is if Google somehow forces vendors to do it.
They are a little more aggressive with iPad and iPod touch deprecation, but I think that’s because some of those devices were built underpowered anyway.
i don't think this is necessarily true.
That said, Treble looks like a good step in the right direction. Maybe things will improve in the future.