I've thought about this myself as I'm getting a HT soon, but won't be getting on fin. Here's why:
1) Obviously the risk of permanent sexual side effects. Life being chemically castrated would be effectively over. There'd be no reason to exist.
2) I'll be nearly 27 when I get it. Let's say I get 3 years before I need another HT, then another 5 years after the second transplant for another, then another 5 years after that for my third and last one (given you have about 6000-8000 grafts that can be taken, you can probably have 3 HT's lifetime). That'll get me to 40, and at that point mostly everyone looks like shit anyway. Even Chad isn't getting college aged girls without paying for it anymore, so fuck it, I'll just shave my head at that point and pay for the pussy.
3) When you're older it's more acceptable to be losing your hair anyway. It's only a true death sentence in your 20s and early-mid 30s.
4) It's possible your hair loss won't progress anyway. A good portion of those guys on fin will be taking it unneccesarily because their hair loss wouldn't have gone further anyway. Similarly, there's some guys fin won't even help as their hair loss is too aggressive.