Who the heck would build a swimming pool thirty feet above ground?

I don't think anyone near here (Michigan) has built an in-ground pool for years; a number of neighbors did years ago, and wound up filling them in. Not usable enough of the year to be worth the upkeep. We have a decent little lake beach in a park just a few minutes away, and it's just six bucks for an old-coot sticker for the season.