An average US smartphone user supposedly receives 46 app push notifications per day. It's highly likely that most of them are distributed during working hours, so if distributed equally an average user is interrupted ~ 3 times/hour during 16 hours when they are awake. This figure is likely higher in some Asian countries, where some apps play integral part in the lifestyle.
Science is clear on the effect of notifications on productivity - it's bad
. Both android and iOS has features to disable notifications for the entire app or by categories, but when it comes to categories the onus is on the app developer to maintain the etiquette.
I think there is a need gap to impose etiquette on the users as well, considering majority of the notifications are from messaging apps and social networks. Making the user select the category of notification e.g. 'delayed' for a meme & 'immediate' for urgent, emergency communication can help this.