I don’t usually like using a case on my phone, but I do like having the option if I know I’m going somewhere where it’s more likely to be dropped: walking around a lot of concrete, wearing shorts/pants with more loose pockets, or travel in general. If I’m gonna use a case, I want it to be as thin as possible to not affect the size of the (already universally too big!) phone.
I also like being able to use my phone with Qi2/MagSafe chargers, which is why I got a Mous case last time…