Alongside casual vs formal I think we see workwear and sportswear consistently evolve into fashionwear. I see the baseball cap as an example of that. Baseball caps were originally worn by players. I think the bucket hat is another example, traditionally worn by fishers and farmers. Both of these hats came in around 150 years ago.

Knit or woolly caps on the other hand have been used for over 1000 years. I think it's safe to think the knit hat will be around for many more generations