Jet engines are loud, high maintenance, and expensive; [...]
Proper jet engines need good maintenance, but they can run for 2-3 years (full on all the time) without or with minimal maintenance. I am talking about jet powered turbine generators/compressors used in remote locations for gas/oil pumping.
Other than that, jet engines are MUCH harder to maintain - your local car shop is not suited for this job at all, this is different league/standards/mindset. Only air plane or jet engine repair shops have required skills and tools.
Difficulty arises from the use of delicate parts, 1000s of parts not suited to be replaced and the fact that one usually needs to strip down the whole engine completely. After repair comes strict procedure of assembly, balancing and tuning jet. You just cannot fix jet engine as simply as a car engine.
[...]Have you ever wondered why only Jay Leno owns a turbine powered car?[...]
Yeah, Jay Leno likes to buy and buys everything that moves on its own power and wheels. He is no example of a typical potential consumer for jet powered stuff.