It should be a trend. I've been wearing a crossbody small bag (I guess you could call it a fanny pack, technically) for a long time now and ever since I've gotten a smartwatch I rarely need to take my phone out, so it lives in the bag instead of a bulge in my pants pocket. I wear the bag in the front so when I do need my phone it's just as quick to pull out of the bag as my pants pocket.
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.
