Unironically there are bags that I used to associate with drug dealers that are becoming common: https://www.jdsports.co.uk/men/mens-accessories/bags-and-gym...

I wouldn't be surprised if discomfort from having a bulky phone in your pocket drives this.

I am also guilty of buying a bag (not this kind) for my phone because it's so much more comfortable (and makes my trousers last longer) to not have my phone in my pocket.