How ironic you guys had the NSAA convention in San Antonio! Haha. My old snowless stomping grounds! I'd have to say that most of the peeps I know didn't return because (A) Cost (they just don't make it a priority), (B) Time (again, not a huge priority to them), and (C) Lack of lessons (see below).
Being that it's so rare for them to actually get out to the mountains, they say they don't want to "waste their time with lessons." Those fools (friends of mine) refused to take lessons, tried learning from a friend (aka another Texan), had a bad experience/didn't really learn how to ski/got injured, which of course discourages them from trying again. I always tell my friends from back home that "Friends don't let friends teach friends how to ski." Saw that on a bumper sticker in CO a few years ago.
Some resorts are really fantastic about promoting cheap lesson packages. I've had deals where you basically just rent the skis and buy a lesson, and get a free lift ticket included, or the other way around. I believe that if people were better about starting their trips out with a lesson or two, they would enjoy skiing much more, and it would make them want to return that much more! Some resorts understand this concept well. Hook a newbie up with some free lessons/lift tix/rentals, and it will not only make them more inclined to return to the sport, but will also encourage them to return to your resort.