Who would want to do this? Security researchers. Why? Because press releases like these are how they get research funding to continue their work.
Now, in a movie-theater mentality, I can think of reasons to do this beyond stealing a car. For example, if I can cause a 30 car pileup on a major highway, that'll draw attention and resources away from the financial district, making it easier for me to rob.
In this case, it has the added benefit of being blind-broadcast. Unlike the Miller/Valasek attack, which is IP based and could theoretically be logged, broadcasting DAB signals doesn't really have any source address, and wouldn't linger any longer than the station had to be up for the attack. Fake signals, crash car, kill target, fade into the night.
Would your ordinary smash-n-grab gang banger use this? Nope. Would it be useful in assassination? Ya betcha!