In the worst cases, I've worked with people who had notifications go off every 2-3 minutes. I can't help but assume this destroys their ability to focus and turns every mental task into a herculean effort as they must backtrack so frequently.

Every context switch makes them forget what we spoke about, or what we were working on. Notifications turn their phones into literal torture devices.

Disable as many notifications as humanly possible, and make it the highest priority to reduce how many times per day your phone interrupts you.