Really only a handful of things:
-
navigation while traveling - don't need it much, if at all at home, but I travel often enough for work that losing that capability would be painful.
-
MFA - authenticator apps are the most convenient way to do MFA. SMS/email are terrible options for this and should only be used if there is absolutely no other option.
-
Access to the internet while away from home, both while traveling and while out and about
-
Music playback in the car
-
Communication - most of my friends don't use SMS/voice to talk, instead preferring Discord or Signal
Basically everything else I do on my phone could be done from a more proper computer with minimal inconvenience.