Flight training is fairly hard work. That is, each flight (and the
study to prepare for the flight) is physically and mentally tiring,
even exhausting. This actually appeals to a few geeks who like the
challenge, but the majority of people will be shocked at the work
required. This is very unlike high school and even college where you
can coast by most courses. Furthermore in school there is only
abstract feedback, a score on an exam or term paper. In an airplane
you get real feedback very quickly when you screw up.

Even today I remember the strange feeling around my first solo,
realizing that I couldn't just stop driving to rescue myself; if I
felt suddenly afraid or ill I would have to work several more minutes
to get myself safely to the ground.

All of this is very foreign to the young generation coming of age and
wealth. They're used to TV dramas where everything is resolved in an
hour, or video games where if you screw up you just hit reset. That
mentality doesn't work in flying.

Jay is right: money is not a real cause for dropping out for most
people, but it is a handy excuse. The Sport Pilot will help some, but
with people in post-industrial America and Europe being raised to
avoid risk and not make their own decisions, flying is a strange world
to enter.