They were invented by Robert Kearns, who was an inventor working independently, in 1963. He shopped the invention around to Ford, who didn’t buy it from him, but conveniently six years later starting selling cars with the feature.
He then acted as his own lawyer in a 12-year court case, and finally won one of the most famous patent infringement cases ever in 1990.
Some of them used a bimetallic strip / heater coil timer, just like “thermal flasher” turn signal switches. I wouldn’t be surprised if thermal flashers are still used on cheap motorbikes, they certainly were in the late 1990s.
It’s partly just convention on ICE vehicles anyway. Some older vehicles had gear shifts on the steering column or the dashboard, and apparently the current Fiat Ducato van has a dashboard gear lever:
So, technically, my truck has two bench seats: the rear seat is a ‘normal’ bench seat, but the bottom’s split to allow the two parts to be folded up for storage access. the front has two regular seats, and the console in the middle flips up for a third ‘jump’ seat of sorts. I’ve used it in that configuration a few times in the ten years I’ve had it- normally it’s in the console position.
All six positions do have seat belts, though.
I had an armrest on my 1974 Citroën DS 23, which I owned between 1998-2003. I miss that feature tremendously. Not only did it have a centre leather armrest, there was also a leather-faced armrest moulded into the door panel.
When I win the lottery/get an insane promotion I’m going to convert a DS to electric power, retaining the hydropneumatic system that made it the best riding car of all time (to this day, Rolls Royce licences the technology).