Aside from, y'know, downloaded stuff. That said my phone lasts so much longer in airplane mode, it's ridiculous.

Eh, I fly a lot and never switch it off

The last few flights I was on I didn't notice them telling people to put phones in airplane mode, in contrast to years ago when they made a big deal about it. During landing they said to put laptops away but that small electronic devices could still be used, so if someone wanted to be on their phone the whole time nothing's stopping them and no one is checking if it is in airplane mode. Although it would be pointless for most of the flight anyway because there is no signal. If you wanted to use the in-flight wifi, you can turn wifi on while airplane mode is on and that will work.

You only really need to do it for take of and landing.

But you still don't have data or GPS or anything and a lot of flights don't have wifi so pretty useless unless you have offline games or downloaded shows/movies/audiobooks.