Can give one example. My brother GF, according to my brother, literally can't cook. Like boil an egg is hard enough.
On the other hand he does cooking good (He once baked a pizza in 15 mins....I was like what is this black magic), and teach me over the year's ^^ Since I live alone and value propor food, I haft to learn to cook as well. My brothers GF never really had that need, so it also boils down to that + interest's.
but yea, I often see that people who can't cook and live alone are also unhealthy...it goes together.