DHT expression in the scalp

I have a question regarding the mechanism of action behind androgenetic alopecia. I see some people saying that we lose hair as males with pattern hair loss because the scalp hairs are more sensitive to DHT in the area of balding (pattern). I also read that some people say that the conversion from test to DHT (via. 5AR) is greater in the scalp tissue than in other body parts. This begs the question: why would you ever need to block DHT in the whole body by using oral meds like fin and dut If the “problematic” test conversion happens in the scalp tissue, then topical dut/fin or a topical anti-androgen should be enough ? Anything I am missing something? Thank you!

Hair loss occurs in males because we carry the genes for hair loss, and our DHT hormones trigger hair loss. The genes are programmed to determine when hair loss starts, but most men get it before age 26. I have seen men develop hair loss as late as in their early 50s, but this is an exception to the rule. If we decided to cut off your testicles, I doubt that you would have hair loss, but that is an extreme approach to reduce the impact of DHT. Topical finasteride goes through the skin and into your body as it gets absorbed through the skin/scalp.  You might as well take the oral finasteride. There is a type of liposomal topical finasteride where most of it stays in the scalp, but this is expensive and only covers part of the scalp.  If you spread it around the scalp, it raises the cost considerably.