Google itself is a superapp at this point as you only have one account. But to answer your question, I think it’s because of interoperability issues. Why can’t my calendar services message me? Or why can’t I quickly create an event inside a chat? If you remember PDAs, they fell under the definition of one ecosystem to manage your communication and time, but now you have several services that refuses to talk to each other. One of the core strength of Apple is that kind of integration. It’s not that you want one company managing it all, you just want an integrated app ecosystem.