with our 15 year old son it allows him to make last minute plans and let us know what’s happening and then we don’t worry.
for our 10 year old daughter, larlegly because her big brother has one originally but there are a number of after school activities she does and being able to communicate via text etc has been very useful on occasion.
neither use their phones to text/call us much tbh.
neither has had the thing confistcated so one can only assume they’ve been sensible about them during the school day.
yes we could cope without but, then again, why should we.