You seem to be highly informed about the topic, so can you explain why don't they do something about it?
Do they not have enough money to invest into the matter? Are they try to protect someone? Do you have any proof to present to us, maybe?
Because there is no pressure on them to do so. 95% of tennis fans think that the current system works and that tennis is a clean sport. There is no heat on them coming from the media. Why change anything? What is there for them to gain?
Perception is more important than reality. Everyone thinks things are fine, until it becomes obvious that they're not. MLB and cycling had terrible doping regimes for years and nobody cared until the major scandals started happening. Then it became completely obvious to everyone that doping was rife, and the only way for them to recover any credibility was to get tough.
Unless high profile players are willing to come out and tell people how pathetic the system is, tennis will be exactly the same. Nothing will change until there is a major scandal, and when that happens then it will be too late. Tennis's reputation as a clean sport will be irreparably damaged.
I don't want to see that. Do you?