1. It's not a disease because it is in essence a secondary sexual characteristic found above all in whites and Semites and mixtures of the two.
2.It has always been around since the beginning of written history.
3. It is correlated with both sexual maturity and beard growth.
4. In terms of terminal follicles, for some men, beard growth can equal scalp hair growth.
5. Because we see such sexual dimorphism all over the mammalian kingdom.
6.Because it is not associated with any immediate health conditions that threaten life.
7. Because it is generally untreatable historically and associated with acne, dermatitis and other DHT artifacts.
8. Because for some people, baldness is an improvement to their crappy, frizzy unkempt hair and is much neater and more acceptable in a corporate or formal environment.
9. Because you are conflating physical health with psychological distress or dysphoria.
10. Because it is an artifact related to male dominance, not male inferiority.
11. Because it might be linked with greater fertility and larger organs of fertilization ensuring survival of the gene.
12. Because for most men, it occurs well after the beginning of the ability to breed, hence many or most men only experience it after successful breeding.
13. Because it is associated and correlated with increasing age like wrinkles, sun spots and other artifacts of increasing age.
Welcome to post-industrial society where males are generally not needed anymore except for math and the sciences and music. Chicks do all the rest better with less fuss, recklessness, aggression and violence.