You do realise the only reason iphone retina screens became a thing was to enable double pixel scaling because iphone apps at the time were coded to a fixed resolution.

That's the definition of a compatibility hack.

Of course apple being apple they managed to sell it as a feature and made every person who was happy with a 1366x768 laptop suddenly desire a retina display.

- they care about their apps not being evicted from memory as quickly when they switch apps because memory isn’t taken up by 32 bit and 64 bit versions of shared libraries.

- increased battery life by not having as much RAM - yes RAM takes energy.

- using the die space saved by not having 32 bit instruction decoding means you can use that die space for enhancements that users care about, and decrease the die size to make the phone more battery efficient

- for Mac computers, you have computers that are faster, have more than twice the battery life, are more memory efficient (meaning less swap), and can be fanless without getting hot.