Even if they set an alarm, that is a lot less distracting than the phone being able to ring at any time. Besides, any time I set an alarm, I’m already aware of approximately when it will go off and the alarm is just to pinpoint the exact moment. Ie if the alarm is to go off at 2pm, I don’t think about it until maybe 1pm or later as the time starts to approach.

One known and pre-timed distraction is a lot less distracting than many unknown randomly-timed distractions.