Really depends on the use habits of some people. I use my phone for long uninterrupted periods then leave it off for many hours, so in that case I use 30 minutes and it doesn't disrupt me. It was moved from 72 to less since a value less than that would not get in the way of a lot of people. We consider the default reasonable.

I think my super low time is due to me not having socials where I require constant notifications though.