It's a constant cost-benefit struggle. AWS can do it because they are printing money printers.
Sure, this does not excuse most traditional big corps that have huge internal engineering budget yet force a top-down rigid inefficient structure. (Though again, it takes a very principled way of doing things to be able to scale out and keep things sort of consistent and coordinated.)
I get it -- it's such a trap to say, "well, <tech giant> does it!" But in this particular case, I actually think they're walking the walk of having small teams that act like startups. You end up with small engineering teams owning a tiny little bubble, and it does a LOT to keep complexity down in terms of what one team has to manage.
(This is of course much more true for greenfield projects, early stage stuff. Of course the giant services are large and complicated.)
Sure, this does not excuse most traditional big corps that have huge internal engineering budget yet force a top-down rigid inefficient structure. (Though again, it takes a very principled way of doing things to be able to scale out and keep things sort of consistent and coordinated.)