I've seen it argued that the best way to create lightweight software is to give devs old hardware to develop on.
Which, yeah, I can see that. The problem is that as a dev, you might have some generic best practices in your head while coding, but beyond that, you don't really concern yourself with performance until it becomes an issue. And on new hardware, you won't notice the slowness until it's already pretty bad for those on older hardware.
But then, as the others said, there's little incentive to actually give devs old hardware. In particular, it costs a lot of money to have your devs waiting for compilation on older hardware...
Yeah, we just have two ear canals. Stereo is basically all your brain will get.