You just have to look at who is advertising what on TV ,posters etc aimed at men, to see celebs and non celebs with full heads of hair.
I would imagine this has to do with as much positive advertising for their product as possible.
White smiles ,chiseled good looks and low and behold full heads of hair go a long way to sell products to the masses.
Historically it has always been the case that the ideal is projected rather than unfortunately the reality.