Some owners presumably just love basketball.
But there's another reason, one that is blatantly real, but that owners will seldom acknowledge: It's the ultimate fan experience. If you're the owner, you get to hang out in the locker room. You get to hang out in press conferences. You get to sit courtside, within earshot of timeouts. You get to slap five with players in key moments of games. You get to invite people like Julius Erving to hang out with you -- and they show up.
There are not a lot of ways to get into that exhilarating swirl of sports and celebrity. There are not a lot of ways to look so cool.