Hahahaha! Look at those lame ground people machines!
Essentially, creating flying cars of private and commercial-use would pretty much mean giving every man and woman access to a private plane. Think about it, do you want your crazy uncle Tim flying a plane? Flying cars would become a threat to the general population's security, and it would be impractical to build and use.
In real life, a single car crash can destroy a few stores, or cause a large traffic jam and kill tens of hundreds of people at most. Imagine a flying car crashing into the side of a skyscraper, imagine the thousands, if not millions that could be killed or injured.
Will someone think of the children!
If we created flying automobiles, they probably wouldn't be using little solar panels to power the vehicle, whatever we may use in the future to fuel our flying cars most likely won't just evaporate into water and suddenly become jolly and good. Gallons and gallons of most likely combustible and possible toxic fluids would be leaking everywhere on top of a exploding skyscraper. Environmentally-wise, the fuel that flying cars may use would most likely not be beneficial to the environment.
The future is powered by inedible kitchen grease.
If everyone had access to flying cars, a terrorist could easily take a hold of one, and take down almost any building in the world. If we wanted to prevent that, imagine the cost to reinforce or rebuild/redesign the millions of buildings in the world, just so you could have a flying car. Whats that? Why not put a safety feature to simply prevent the cars from going towards a building? Well in the world in general, if you can build something, someone else can unbuild it. In other words, there will always be hackers that are a little bit smarter then the other guys that can bypass it. So at the end of day, it's essentially is selling a flying missile with a padlock on it.
100s of years of technology.
If we can get pass the terrorist ordeal, let me ask you a question. Have you ever seen a real plane cockpit? It's not just a steering wheel and a few pedals and brakes right? We can both agree not everyone in the world is a smart guy/gal, imagine putting crazy Bill behind the controls of a 747 aircraft, let alone a personal hover craft.
Picture unrelated.
Let's say we require a licenses to prove one's proficiency in the use of a flying car. Normal car licenses usually stops people that can't drive from driving right? It works 100% of the time right? Think about all the underage drivers in America alone, instead of crashing your family car into a fire hydrant, your cute little teenager would be crashing into large industrial sized buildings (because why not?), killing hundreds of people in the building, and standing under it.
You don't see big business buying commercial planes for few thousand dollars. They spend millions of dollars to buy those big buggers, so why would they sell it to you for a for a can and two bricks? Don't think that in the future, as it becomes more evident that natural resources are depleting that you'll be buying a hover car for a few cobs of corn.
Weather-wise, if you've ever drove a plane, you would know how much a bad storm can make your journey fifty times less enjoyable. If a few seagulls suddenly found its way into your engine, you'll have a not-so fun crash landing as they take down your engines. There have been many recorded cases of engine failure due to birds getting sucked into the engines of a plane. Imagine hundreds of flying cars lined up in a aerial interstate with a large storm passing by. All the cars swaying around in the wind as the winds pick up, and all it takes is one to flip over, for a a giant vortex of wind, metal, and people. Wind doesn't just push down, it pushes down, then around, a little disruption could flip the entire thing over and spin around in a crazy mess.
Seagull's #1 target.
Flying cars would be too expensive, and if accidents occur, they become a hundred times more dangerous. Even if someone could afford one, and was able to operate the vehicle, daily maintenance would cost a lot towards your pocket, and the environment.
Sorry to ruin the dream of driving to your future job as being CEO of Skynet in a hover car, but it just ain't happening.