Cases are like clothes or jewelry, they often are chosen because they appeal to the user in some sort of aesthetic or fashion sense. This is particularly noticeable with women (who make up oh about 50% of the world's phone users).
It's not just about protecting your phone from damage.
Now if you don't like the looks of these cases, that's fine, but it's not really your choice. In the same way, I find most of the clothes that most of my fellow Americans wear to be relatively unflattering and uninteresting. But if it works for them, great.
One thing I have noticed is that as a whole smartphone cases are stupidly overpriced in the Western Hemisphere. I always gravitate toward clear plastic cases like this:
It's $13. In Japan you can find a comparable case at a 100¥ shop like Daiso, about $0.70 at the current exchange rate. And you visit a shop like Yodobashi or Bic Camera and they have hundreds of designs all priced far below their Western equivalents. And boy do the Japanese know something about screen protectors.
Anyhow, the reasons for buying a case aren't always about protection in the same way with clothes. And like with clothes, it's easy to change a phone case. I know people who have a couple for their favorite sports teams when they're in season. And for sure younger users would change these like Fortnite skins if they had the money.
Wetsuit companies sell pink ones to women not because they insulate any better. It's because some of the buyers want color options beyond basic black or dark grey neoprene.