No one is talking about Face ID, why? It strange that both my iPad Pro and iPhone have Face ID but laptop doesn't, and it's the most expensive device I have.
It's not the expense so much as the z-height. Apple likes their lids thin and weight balanced. Windows Hello exists in a lot of laptops, but I think all of the lids are thicker, usually matched with a touchscreen that had already added z anyways.
There will be thinner faceID implementations, but right now the word is that's for post 2020 iPhones.
iMacs though? Zero excuse not to add it on the next refresh.