I've uninstalled lots of apps when they've sent coupons via notifications. Notifications are to notify me about things I need to act on. They are not a marketing channel. So, yes.
That depends. A business that uses notifications for marketing isn't one I want to do business with. If there's a decent competitor I'll switch. If there isn't then I'll decide to begrudgingly put up with it (and probably complain a bit on social media) or to do without it.
So far I've never put up with it and always either switched to a competitor or abandoned the whole thing.