Every good mechanic in the 70's needed to move a car around the shop
and the trick was that you could buy a junkyard seatbelt plug-in for almost nothing.
People who rebelled against govt control also bought them attached to junk seatbelts
to avoid wearing seatbelts.
Some people made a jumper wire and permanently disabled the solenoid under the dash.
Some people cut the wire under the seat that detected if a person was sitting there.
It's possible that law enforcement had something to do with abandonment,
since police could not start the car for pursuit without their seatbelts plugged in.