None. Ever.
I prefer the phone to feel good in my hands. The phone designers do a lot of work to make it feel good and easy to grip. I couldn’t imagine dropping my phone. I’m an adult though and I’ve taken a lot of time to really hold my phone properly (learn how to grip it). I can definitely understand if it’s a phone for the kiddos or something, then definitely understand. I have definitely dropped a lot of phones in the past though whether they were on my legs and I get up quickly or just dropping it in a silly way. I have not dropped my current phone and haven’t dropped one in years.
Phone cases make phones feel cheap as well as making it feel outdated. Like adds a bunch of thickness to it so that makes it feel old. Also makes the phone look much worse. My phone looks so much nicer than all the other phones people have around me even though they have the newer models.
If I was going to get one though it would most certainly be something made from goatskin leather.