My longer response yesterday got trashed when my wife turned on two air conditioners and tripped the circuit breaker, but here goes:
I think one basic reason is that, unless you know you’re going nowhere in football, the requirements to get in the sumo world just aren’t worth it. Unlike baseball players who come to play in Japan, they’d have to start at the absolute bottom level (down with the fifteen-year-olds), and get by exactly as a Japanese wrestler would.
There’s no citizenship requirement (to get in, anyway), but there is a strict langauge requirement. Recently the Sumo Assiciation added a rule that foreign wrestlers had to pass the level 1 Japanese Proficiency test (near-native fluency. I’ve been here eight years and am just barely at level 2). None of the American stars (Konishiki, Akebono, Musashimaru) reached that level until several years of wresting, prompting some to accuse the SA of reacting to foreign successes by trying to shut them out. With both yokozuna positions now held by foreigners and more scattered throughout the divisions, that criticism has faded, but it’s still a a big obstacle to breaking into the sport.
Also, the pay is shit until they hit the big time. They would have to start at the Jonokuchi level, then fight their way up through the Jonidan, Sandanme and Makushita divisions (which would take at least a year, probably two) and reach the Juryo division before they’d even start earning a salary. Until that point they get just training, room, board, and an allowance of a few hundred dollars a month, in return for which they have to cook, clean, and wait on the higher ranked wrestlers hand and foot. Not exactly glamorous.
About Asashoryu and the hair-pulling, it happened so fast (Kyokushuzan was already on the way down), it looked to me like it was an accidental grab rather than a deliberate cheat. Still, it’s the first time in all the years I’ve been watching that I’ve seen anyone called for an illegal move. The coaches and elder wrestlers are usually so strict about punishing anyone who sets a toe out of line, either in a match or in practice, that it just doesn’t happen.