Look at how much publicity his nothing-comments about doping have received. Can you even imagine how big a story it would have been if he'd come out and said "testing is 20 years out of date, the system's a joke, it needs to change"?
The guy has massive influence.
This might be naivete on my part, but can we be certain tennis players are even aware of the deficiency of the doping testing in tennis? Several posters here are very knowledgeable on this subject and wish to see tennis in an as clean state as possible (and I salute them for that), but to assume the players themselves possess this knowledge is overly cynical in my opinion.