Well, it seems to me that for the pros, a small performance improvement might be meaningful for them. Also the expense of the drugs is not a big issue for them considering riding is how they make their living.
However for recreational riders, most can achieve very large gains by doing things like training, riding, losing weight and so on. Why even bother with something like performance enhancing drugs when these other avenues are such low hanging fruit?
But for me, does it really matter if I get up the hill in 22 minutes instead of 24 minutes? No one is going to give me a check no matter how fast I go. I know, there are considerations of ego and competition but I have long since come to the realization that there are other people out there who are stronger, faster, more powerful and more skilled than I am no matter what I do. The main thing is to have a good ride and gain satisfaction from that.