Because it was outlawed for a long time, and because China has only recently developed major professional sports. It is a lot like the increasing number of European basketball players in the NBA, a decade ago the Euroleague didn't exist in its current form, as such many of these guys weren't true pros.
The fighters can't go pro unless the government lets them, and they just started boxing 10 years ago. Give them time. Supposedly they're going to let some of their top guys go pro after the 2012 Olympics, and they've been working with Gary Shaw to that end. They do have one decent pro (http://boxrec.com/list_bouts.php?human_id=366951&cat=boxer). There's one amateur they have at 108 who will be a good pro if they let him go pro, but he hasn't yet.
Its still a developing sport, most Olympians stay Olympians and China is the land of kung-fu not an European/American Sport. But, there is promise, the World's best female middleweight is Wang Ya Nan who is from China.
LOL @ you thinkin' 2 gold medals won by the Chinamen at an Olympics hosted by the Chinamen w/ subjective scoring actually means something. P.S. Winning a gold at the Olympics doesn't mean diddly squat as far as professional boxing is concerned. All it guarantees is that the winner will be a serviceable pro. He may go beyond that, most times not.
maybe they are all playing american football or in the nba? :hey Im sure if the Chinese decided to do more boxing they would be as good as any other country..its just not their thing..
Over there anyone displaying the natural gifts for boxing such as tremendous reflexes, good hand speed and hand/eye coordination, are forced into other pursuits. Namely table tennis...:yep