They all did this for different reasons, right? Google, I'm not sure about. Block: because their other brands are really tied to particular things, like Square is super tied to payment processing, there's no upside to using it elsewhere. Facebook: trying to break into new markets as Facebook is hard, because everyone knows Facebook is fundamentally bad.

I guess every company that rebrands has a specific reason to do so. Apple hasn't done anything to soil their name too badly, so they don't have to.