Granted, the word stereotype might be wrong. I just wanted to point out that the majority of Caucasian men may be able to grow thick beards but not all of them. As far as Asian men are concerned, most cannot but once again not all of them. That's the generic genetic lottery part. (edited)
As far as testosterone is concerned:
https://en.wikipedia.org/wiki/Beard
The beard develops in human males during puberty. Beard growth is linked to stimulation of hair follicles in the area by dihydrotestosterone, which continues to affect beard growth after puberty. Dihydrotestosterone also promotes balding. Dihydrotestosterone is produced from testosterone, the levels of which vary with season. Beard growth rate is also genetic.
So beard growth depends on the person's genetic makeup. And on testosterone. This has nothing to do with American bro culture thinking. Female athletes who were given testosterone as doping post WW2 could start growing facial hair if their genes happened to be right. You need the genes and the hormones.
Edit 2: I have a feeling some of this disagreement we are having may be due to my repeat typo generic -> genetic. Written on my phone and didn't notice the one letter difference.