Individuals in their 20s with normal testosterone levels should not take exogenous testosterone, with rare exceptions.

“Not many cases. The reason for any performance enhancing drug, whether or not it is a steroid, synthetic, bioidentical, or otherwise, varies a lot. Some individuals do it only for cosmetic reasons even if it can have deleterious effects on the cosmetic appearance, for example, of your skin in the long run. But everyone has their different reasons. As far as like when does the benefit outweigh the detriment, not very often if you're in your 20s and certainly-- probably-- almost hardly never. There's always rare cases, like Coleman syndrome and whatnot, but almost never if you're very young.