If the top players are so great and talented, they should be able to show it in every type of conditions. The real reason why courts won't be sped up any time soon is because, for marketing purposes, it is in the ATP's best interest to preserve the untouchable image of the 'Big 4' and not expose them as the one dimensional baseline grinders at least 2/3 of them are.
Am I the only one who would like some variety? If the top 4 was gone and changed fairly often I'm sure more people would like Men's Tennis. I heard TF is getting more traffic than MTF and I'm fairly sure that the reason is that they have new top players every 1/2-3/4 a year.