I wonder why there are so many doubles specialists in badminton. in tennis and table tennis there are some "specialists" too but most top tennis dubs players have been top50 singles players at some point or at least top100 (which is probably like top30 in badminton given the higher "professionalisation" level -i.e more players making money). however in badminton most players seem to be specialists. why is that? are there any players who are world class (say top50 at least) in singles and doubles? or have there been such players in the past?