Why? Imagine a vehicle that in practicality performs the exact same job as a helicopter, has the same or actually worse failure modes than helicopters(helicopters can at least autorotate, most proposed "flying cars" can neither glide nor autorotate) and now tell me why would such a vehicle have any lower maintenance requirements? Sure it might use an electric motor instead of an engine, but surely safety would require the exact same maintenance regimen as an actual helicopter. This is not going to be a car that you can bring for an inspection once per year, pay £30, change some oil, cabin air filter and be done. It's going to be as costly as any other air-worthy machine to own, in which case any kind of comparisons to a personal car are frankly out of the window, and anyone who thinks they could build a business around one could build a business right now using existing machines. That's not to say that innovation shouldn't happen, quite the contrary - but the whole talk of "flying cars" for your Joe Shmoe is just a pipe dream.