Why can't the OS just be an OS though without ads anywhere? Clearly if you install firefox you want to use firefox, otherwise you'd switch back to safari.
Because ads is the only way to make constant money from consumers if you don't sell hardware with the OS. That said, not all notifications are ads. Sometimes, a notification is just a well-intentioned notification that only a small portion of users take offence to. I bet that if they made a "Safari Rewards Points" program that would annoy the hell out of everyone.
