Instant messaging apps don't need notifications either. It upsets some people at first, but it is for the most part perfectly fine to just check and respond messages in your own preferred frequency.
For me this becomes worse: If I don't get (reliable) push notifications for things I want updates on, I tend to become obsessive over checking it. The more different things I am checking this way, the worse it becomes in terms of disruption to my focus. Push notifications unify multiple streams together and let me go 'I don't need to check this, I'll get a notification if there's any update'.
I could agree: it always depends on personal preferences or usage scenarios. Even I have some IM apps' notifications disabled and I check them only once in a while.
But some IM I treat as a really instant communication channel with my family: I don't want to miss any message from my kids or "I am at grocery, do you need something?" from my wife
