Secondly – middle aged spread (especially, for middle-aged men – as aging tends to come as more of a shock to men than to women.
As kids, we all grow up running around all over the place, chasing each other, playing multiple sports and activities, and are generally pretty fit and healthy. Then we leave school and go to Uni, or entry level jobs; and… we're not chasing each other around the playground on break, and we probably only stick with 1-2 sports / physical activities. The variety of challenges we expose our bodies to, is reduced. Then into our later 20s and early 30s, girlfriends/boyfriends become wives/husbands; cats become dogs become human children, and we get a couple of promotions at work. A lot more demands on our times, but no more time in the day, so something gives way – usually exercise. Additionally, with a little more age, we recover from injuries (including DOMS) less well. We go from training twice a week and playing every weekend, to playing only, and not every weekend. But we keep eating as if we're burning those 5000 calories a week that we used to. Our body composition changes and we develop middle-aged spread. Which exacerbates an element above about injury recovery, and likelihood. Injuries here tend to be forgetting that our body isn't 20 and invulnerable anymore (you can't lift that, but you haven't realised yet - or at least, you can't lift it with lazy technique)
NB: Women also follow this exact same pattern, BUT… Women tend to be more bodily aware than men, and women are a touch more involved in the process of growing a foetus (and stereotypically, with growing the subsequent child) than men. Even if women weren't more bodily aware than men, their body goes through a dramatic, and undeniable change, with a decent amount of support based around shedding that weight afterwards, and the problems their body will present them with.