Not to get too philosophical, but basically technology has a huge part to it.
Our generation (the young'uns), have grown up with a lot of technologically advanced stuff. This allows for communication etc. over the internet, and has thus HUGELY minimized our human to human contact. Given, this isn't true for everyone, but it is very true for many people.
Technology has also made it a lot easier to learn magic. This means there are a huge number of people that know magic, but we still don't see that many people out performing. People learn the magic, master the sleights, but are then afraid to go out and encounter actual people. As stated previously, it gets pretty boring mastering a sleight,
especially if there's no one you're performing for.
Flourishing is an art in and of itself. It is able to be enjoyed by the performer, or any spectators. Not discarding the rewarding sensation of mastering a flourish and all of the other things flourishing does, a large part of XCM's popularity comes from the fact that people are becoming more afraid of people. It's easy, ironically enough, to sit in front of a computer screen and do whatever, but human interaction adds entirely new elements.
Dan and Dave, clearly a, if not the, driving force behind flourishing will be the first to admit that their presentation is what they've been lacking in. I actually spoke with the owner of a magic shop over in California who said he knew the Bucks as kids, and always saw them, heads down, walking around practicing their flourishes. They were shy, and flourishing provided an entertaining way to amaze with cards without the "awkwardness" that magic can cause.
Does this even fit here? And wow, this was a lot longer than I'd thought it would be
Oh well, just my two, or three, cents.