I'm probably completely missing the (presumably relatively common) scenarios you have in mind where stolen cars are used for violent crimes. (I'm assuming reckless joyriding isn't what you're referring to as "violent crime"; maybe that's my issue)

If you want to go commit a violent crime, and have motorized transport, and not be caught. Then it is helpful to have a vehicle that is not tied to you.

Happens in places like New Orleans. Some gang members steal a car, go shoot up a neighborhood, and ditch the car.

> I'm assuming reckless joyriding isn't what you're referring to as "violent crime"

It is, and worse. There have been numerous cases of scumbag teenager stealing cars and then crashing them into people, mostly by accident but often enough on purpose. They also use the cars for gangbanging shit since they know the car can't be traced back to them.

A lot of this stuff wouldn't be happening if cars weren't so easy to steal. There is a casual accessibility to stealing certain cars which makes it an easier crime to commit than carjacking (parked cars aren't witnesses, parked cars won't fight back or pull a gun of their own, parked cars won't try to run you over, etc.) Once the car is stolen, other impromptu violence seems and becomes easier.