I guess having only one phone every year makes it immensely easier to support than having multiple models at every price range every year. Apple does it, why couldn't Android phone manufacturers do it?
Also we need to consider how phone companies differ from Google and Apple. Those two also generate money off the users purchasing apps and etc, and they have the ability to push users to their services easier. Where as strictly phone manufacturers make money at the sale of the handset, so -- as you put it -- they're incentivized to have as much penetration as possible by selling as many models they can.
Tho, I do think people are starting to care about support length as the phone market matures and people wait longer to buy their new phones. Which is why, I think, Android manufacturers are lengthening support (and not out of the goodness of their hearts)
Please educate me if I'm wrong, but doesn't Apple's model of continuing to sell older flagships, or even reusing old chassis and putting flagship chips inside them cost less money in the long run? I imagine the price for manufacturing the same phone 3 or 4 years later would cut down significantly, no? And by doing that, you also won't need to spend R&D money on extra models.
Oh indeed! That helps as well. I imagine other manufacturers do this too, but I only follow Apple closely since I was a huge fanboy half a decade ago. So I can't speak with certainty for them
Apple does it by introducing new models while lowering the price of older ones. That effectively covers the lower budget price tier while not having to make a whole new model for it.
It's at least getting better. Samsung, who had a much wider range of phones, moved to 4 years of security updates. Pixels moved to 5 years. Too many other brands to list their support length too. Apple still beats them though.