Modern cars will usually warn the driver if there’s a door open or if one of the passengers isn’t wearing a seatbelt. But that’s for the safety of those inside, even if sometimes it can be a bit annoying (wear your seatbelt, folks!).
However, if somebody were to get a salvage vehicle that will be transformed into something completely different, all the various sensors that monitor doors, seatbelts, airbags, and everything else might make the car undrivable after the things they’re monitoring aren’t there anymore.
