Privacy advocates got access to Locate X, a phone tracking tool which multiple U.S. agencies have bought access to, and showed me and other journalists exactly what it was capable of. Tracking a phone from one state to another to an abortion clinic. Multiple places of worship. A school. Following a likely juror to a residence. And all of this tracking is possible without a warrant, and instead just a few clicks of a mouse.
Depends on where you are really. Small towns everything is cash or a phonecall to a person from any phone (it’s really like stepping back in time about 15 years) but in larger cities you might find yourself required to use an app to unlock your apartment or office door or buy a train ticket or pay for a parking space, or buy a bus ticket or hail a taxi. In work I’ve needed a phone for 2FA in my last 3 jobs (granted in IT that’s probably for the best) and in college they distribute resources on the school website via big in-person QR codes.
While every single one of those things almost always has a non-smartphone option, it increases friction significantly, and then you’re the annoying person who is slowing everything down by not doing something the way everyone else does, however in a workplace they’ll often simply provide you with a phone because that’s easier than going to the trouble of ensuring every edgecase is covered and ensuring fair compensation for requiring you to have a phone.