Why is that anyway. Professional level badminton and ping pong (AKA table tennis) is AMAZING to watch!
I guess they figure people don't watch them. In the US we've got a weird chicken/egg situation where they give us all gymnastics/track/swimming/diving because they say that's what people want to watch, but that's all they show during "convenient" hours so that's all people watch. And beach volleyball. There was a LOT of coverage of rowing, for some reason as well...even though rowing actually makes for pretty boring television. Yet they showed very little whitewater which is far more fun to watch than flatwater rowing/paddling.
But then these offbeat sports that you don't see every day and are a blast to watch...if you catch them at all it's during off-times.
We get somewhat the same problem with winter - heavy focus on figure skating, downhill and speed skating at the expense of other events, but the relatively small number of events makes it less of a problem.
Annoying thing is the success of curling over the past 2 winter games has showed that if you give people a chance (and solid knowledgeable commentators to talk the viewers through like Don Duguid and the late Don Chevrier), they might come around!