Genes.

Far Eastern Asians generally have less body hair. Not just men, not just facial.

Other people do too - the reason I gave up growing a beard. Can't get beyond the scraggly phase.

More reading:

https://safereddit.com/r/explainlikeimfive/comments/1l9525/eli5why_do_asians_usually_have_no_body_hair_and/

many of the distinguishing features of East-Asian people have recently been linked to a single gene mutation.

edit: Far Eastern, not all Asians.

They also have funky other differences like dry ear wax, non-stinky sweat, they turn bright red when drinking alcohol and a lot of them have blue-ish birthmarks.

It's fascinating what genes can do! Just like sneezing when looking at a bright light or having the coriander=soap gene.

I read this and immediately thought "well, that's completely wrong".

I'm British, so to me "Asian" usually means from the Indian Subcontinent. Some of those guys can be very beardy!

Anyway, the answer to your question is a phenomenon called Neoteny.

Basically, it's the retention of juvenile characteristics into adulthood. It occurs almost exclusively through sexual selection.

In East Asia populations, there is a mutation in the EDAR gene which is associated with the specific differences you've mentioned (along with thicker head hair, less prominent chins, smaller boobs, etc).

Anecdata: i am Eastern European, and can't grow a beard. Like, I am trimming it once in couple of weeks

i have the shave mines every week, but i dont grow a thick beard, i also get cheek hairs. asians do grow straight hair and its faster growing, because of how the follicles are orientated.