I really don't think it's about availability or advertising.
I have a friend, about 50, makes a good wage, has a house in the country with room for a landing strip and works at an overhaul shop. Been around planes his whole life. He's thought about learning to fly, but even though he has lots of money, he can't justify spending it and taking the time to do it. Figures he wouldn't get enough use out of it.
I live close to a private airport. About 40 hangars and around 30 planes tied down outside. A lot of lifetime homebuilders. Some have four planes in their hangar and can't be bothered to finish one. On a nice sunny summer weekend, you'd be lucky to see two planes in the air at the same time. Maybe five people flying total for the weekend. It's turned into a big social spot. Everybody wants to sit around and talk airplanes, but nobody wants to fly.
This is part of the reason for lack of interest from the public. When you buy $300 sneakers, you buy them to show off to people. Phones and iPads are both a way of socializing and a status symbol. Same with Harleys and cars to a certain extent. Whatever the value these products are to their owners, they can realize it with very little effort. Skiing takes more effort, but it's still an all day social gathering that even someone who is inexperienced can enjoy with their friends without a lot of rules. Showing your certificate to somebody is like a rich person showing pictures of his mansion in Alaska - poor people can't relate and rich people probably don't care. Finishing your homebuilt means flying it and that usually means people won't see it.
Piloting is a relatively solitary activity. Most people will agree that its difficult to find a passenger. Then there is the boring aspect of flying to the same places all the time. Very few people find enjoyment just from the act of being in the air. Going to different places further away increases costs exponentially. A sunday at an average small airport is a few people flying for an hour or so in the early morning, coffee for another hour or so, then the place is deserted by noon. Even if Joe Public lived just down the street and was bombarded with learn to fly commercials, its not exactly an enticing place.
People's way of thinking has changed over the years. It's all about instant gratification. Thirty years ago it was common to take the family on a cross country car trip. Now they fly to maximize the time at the destination. It's not advertising or availability, the car is in the driveway and its probably cheaper for a family of four. Nobody wants to sit in the car doing nothing (such as sightseeing).
Is it even possible to advertise learning to fly in an honest manner and still have the average person want to do it? Imagine the ad.
For only $6000(or more), and a few (or more) months of dedication, you can be be a pilot! Imagine soaring through the sky (weather permitting) by yourself for only $120 an hour (aircraft availability may be limited). Feel the freedom to go anywhere (subject to TFR's), and land at interesting places (landing fees may apply). When you return you can socialize with other pilots (who couldn't afford to fly that day) and share your experiences (not too many as the majority of pilots fly less than ten times a year). Feel the freedom! (subject to background check)
I'd love to see more people become interested in flying, but first we need to start showing some interest ourselves.