What doesn't make sense? The Transition looks fairly OK, though it probably only suits flying to places that are small and don't have rental cars.
Flying car now is a better idea, if they're automated. More complicated flight systems are no problem for software. And safety will be far better than humans. Though if we get fully automated roads/cars, the speed improvement might not be so big. (Automated roads might be able to go at what, 200Kph? More on highways?)
Flying cars are a horrible idea. Flying requires a 20x higher energy output than driving. It's extremely weather sensitive. It requires space for landing, unless you go VLTO, then your energy usage skyrockets even more. There are huge privacy concerns, last mile and noise issues. Not to mention it would be a further move from mass transit to (much less efficient) private transportation.
I'm not sure that's always the case. Take a look at the PAL-V, which is in production right now (there was a short item on it on Dutch TV, they're currently looking for investors to boost international sales).
According to their specifications [1], it can do 6 km/l when flying, and 12 km/l on land. The specs they give aren't directly comparable sadly, so I had to do a short calculation to get the flying mileage (180 km/28 l), but it suggests that your 20x figure is one order of magnitude too high. The vehicle's range also suggests a 3x difference, not 20x.
I just see it as a personal plane that doesn't require a taxi or rental car. If they were more common, then the limited amount of space needed for a light-car runway would be easier to pop in. Also note that Jetsons, to use a fictional example, had no qualms about building up, in comparison to apparently everyone in the West.
Flying car now is a better idea, if they're automated. More complicated flight systems are no problem for software. And safety will be far better than humans. Though if we get fully automated roads/cars, the speed improvement might not be so big. (Automated roads might be able to go at what, 200Kph? More on highways?)