The Nexus 5 no longer works.
The Nexus 4 still works, but its battery is puffing out.
The Nexus S has no hardware problems at all, but it's too underpowered to run modern software.
The model "phone vendors nefariously build products with short lifespans, regardless of what people want to buy, so that they can sell more hardware" has trouble explaining why the longest-lived phones are the earliest ones. It seems more likely that the phone vendors of today build phones with short lifespans because bitter experience tells them that building a robust, long-lived phone is all cost and no benefit -- the phone costs more, it's heavier, it's fatter, and all your customers replace it before the cheaper, sleeker, more attractive phone would have failed anyway, meaning they actually get zero minutes of extended lifespan.
It's the same reason animals age and die.