Why is it not wise to get a hair transplant at 20 year old?

I keep seeing this pop up. I am 19 right now with a NW2.5-3 and just started taking finasteride. My plan is take fin for a year then — assuming I respond to finasteride normally (just maintain hair, am not a non-responder/super responder) — get a hair transplant at 20/21ish. Why would this be such a mistake? The finasteride should roughly maintain my hair for a decade or so, right? I’ll be able to...

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