The American anime industry is a really peculiar thing.
Imagine yourself at Best Buy and you're looking through the DVD aisles. You see a ton of movies. Most people who would buy these movies buy them because they either saw the movie in the theater and really liked it, or they saw a trailer for it or promotions on TV or what have you. Then you have american TV season boxsets. Obviously they've had the opportunity to see the show on TV already and became and fan and thusly wanted to own the boxset. These 2 sections make up the vast majority of the DVDs they sell. A product they have prior familiarity with in some fashion.
Then you have the anime section. Now granted, there are shows here that you could have seen on american TV as well and thusly have the same appeal as a regular TV season boxset, but most of the stuff on those shelves is media that has had no american showing at all, either in theaters or on TV. So it's no wonder that many people who are mostly unfamiliar with anime pass by that section with a certain amount of confusion. "What is all this stuff and why is there so much of it?.. Who is this for?"
Obviously, it's for people like us. People that are anime fans. Then comes the question of, where did you find out about the show in the first place? For many people, it would be because they watched the fansubs. Or maybe in some cases they saw an AMV using the series and that got them interested (I know many people who bought RahXephon for this very reason back in
2003). Or maybe they read about it in NewType/Anime Insider/etc. Whatever the reasoning, it's far removed from how typical consumers normally base their DVD purchases.
So because we can say with some certainty that a large chunk of this small sect of fans first became aware of the show by watching fansubs, we then know that they already HAVE the series in some form. So then it comes down to the base utility of a DVD. It's convenient for group viewing, it (usually) comes with an additional English dub, sometimes they have decent extras. Is this amount of utility worth the purchase? There's also the fan-drive. Maybe we want to support the anime by giving the studios/distributors/etc. our money. Or the fan in us just needs to fill the collection.
My point here is that the buying draw of anime DVDs vs. movies/TV seasons is HUGELY skewed based off of the niche market, the oftentimes lack of familiarity by the general public, and the outrageous leap in price when compared to a normal TV season (which I understand is different due to the licensing & production costs associated with releasing an anime series, but nonetheless, the price numbers are far higher when you compare the amount you pay against the amount you get).
Because of this, I'm amazed the American industry has survived this long. But it's a strong testament to how fan-based this community really is.