On my PC and my phone there are ample opportunities for notifications. Some of them are system notification like charge levels, but most of them come via applications. One could get a notification for every email, every instant message. Browsers can now relay notifications from websites to the user. On the phone you have messages, calls, reminders.
There are the maker and manager schedules. In short a manager works on a rather short time scale and does a lot of little decisions. The maker in contrast goes into the zone and works on a problem with deep concentration. Ripping the maker out of that concentration will result in a loss of a lot of time because they have to get back into the zone again. Notifications are interruptions that are easily turned off.
I differentiate between real-time notifications like calls and alarms and asynchronous stuff like messages. For a call or a reminder I want to know right away because it usually is important. A message can usually wait for a bit. It is nice to know when something happens, but when I am in the zone I do not want to be interrupted involuntarily. Therefore I have disabled most notifications except calls on my phone and all except battery level on my laptop.
On Android I have even disabled the heads up notifications because they overlay over the screen. It basically says that whatever I am doing right now is less important than some message that I got. Instead the icon of the app just appears in the status bar and I can act on it after I am finished with the current task. If I am curious I can still pull down the notification area and directly read it, it just is not the default.
The disadvantage is that I actively have to look for notifications. This way I have developed the habit to check for input even though there is nothing there. With notifications I would only turn to it when something actually came up. One has to weight the false-positive and false-negative rates here. What do I want to avoid more? Being interrupted when I do not want it or spending a bit too much time looking for new notifications when there are not any new ones? For me the former is the one I want to avoid, therefore I have most sounds and vibrations turned off.