I reckon that's because Google largely works on pull models: you ask for something and G gives it to you. Its services superficially appear like databases just sitting there, even if we know that's not the case.

FB and Twitter, on the other hand, largely work on push models: you log on and the app will give you stuff to look at, as well as notifying you incessantly. It easier to perceive the app's own agency and priorities.

In this sense, it explains why Google tends to get heat over Youtube: because it's closer to a push model, both with homepage and suggestions.

Also, Google services are largely useful to get stuff done, in a way FB and Twitter are not. That gives G a big pass.