Just a social norm. Allegedly keeps the water cleaner with less hair and detritus. However, you’re still expected to wear one if you’re bald. I certainly didn’t agree with it. I think it’s more important just to shower up before swimming.

When I visited Spain, they wouldn’t let you swim in the hotel pools unless you had a cap.

Unpopular opinion, but I got used to eating hot dogs growing up with regular sliced bread and I might even prefer it. The bun/dog ratio is good. However, I know it’s more bread and is contradictory, but Danish hot dogs are my favorite.