Off the shelf kits exist. There are also people who specialize in installing them. I think these kits don't take off because the people who are car nuts do some research about what type of performance can be expected from a conversion, and they conclude it would make the car worse overall. Worse performance, worse resale value.

Classic cars are only possible to collect at all because of a lower level of proprietary crap than new cars. If you convert a perfectly working classic car, you're throwing away whatever engineering goodness is inside it to install some inferior bespoke and likely proprietary system. You will probably have to cause permanent damage to the original frame and body of the car. What you end up with is a weird combination that could malfunction in some circumstances, and has inferior range and resale value.