There are plenty of times when you have to trust someone(s) else with your belongings, sometimes for a very long time - say, airline baggage, bus luggage compartment, hotel left luggage, or gym lockers - and it's useful to have a tracker (ideally a more secure one, e.g. AirTag) in case anything goes wrong.

And even if you're the type of person who never lets their bags leave their sight, nobody is immune to their keys slipping out of their pocket in a taxi.