I think about 50% of men suffer hair loss before they're middle-aged, it's just advertising/TV/film tends to make it look like everyone has a full head of hair, the same way women are 'shopped into having unrealistic proportions and chase an unobtainable look etc. You can inherit baldness from any side of your family, it can skip generations and if it's fairly aggressive there is literally nothing you can do about it, although simply removing it and rocking a crewcut/skinhead is way more socially acceptable than it used to be. People with slow/mild hair loss have several options for slowing/stopping/regrowing thinning hair, at a cost.
Loads of people start losing their hair in their teens, their twenties etc. It's unfortunate, aesthetically, but it's natural.