Very soon, cars won't really let you do anything without ID/phone number/paired phone/key serial number, gps lock, a full working complement of vehicle sensors, and a network connection to report all of the above in realtime to people you don't know (who are of course obligated to provide all of that data to military intelligence at any time, without a warrant or probable cause).

There isn't really an issue with that sort of lack-of-maintenance stuff where we're headed. It won't be long until cars either totally refuse to operate in extreme circumstances (due to manufacturer liability), or fall back to some impossible-to-ignore state like Tesla's "limp mode". Tire pressure/oil life being good examples of easily-detectable liability issues that no sane manufacturer would let slide.

The current state of affairs is simply because remote monitoring was expensive/infeasible. Most vehicles today ship with an always-on cellular modem in them.

Even my little 4K pocket gimbal camera won't operate without phoning home to "activate", same for all the drones sold by the same company. Flying cars would be sending telemetry from all local sensor measurements to HQ at pretty much all times.