I would be more kind to them if the general opinion of them wasn't so extremely negative. I see their practical purpose, but I also think they look kinda dumb. Which is a shame, because as accessories go, I imagine they would be very practical.
Maybe the first and foremost problem is that they look extremely cheap, like a downsized backpack, that gets no kind of love whatsoever. Fastened with a plastic clip, it pulls its looks down even more. I wouldn't feel ashamed to wear one if it could be made more discrete, and not so damn ugly. And I don't think I'm metro enough to wear a purse.
I don't like having things in my pockets; phone, key chain, wallet, it quickly becomes crowded, and large key chains are downright unpleasant to carry around in my pocket. I don't like having my wallet in my pocket, it puts a sort of chafe on my pant legs that I don't like, and it gets hot and clammy between it and my leg. If I'm wearing shorts/cargos, the pocket space is either even more limited, or it makes the items in the lower pockets swing around like crazy. I also don't like wearing a backpack when wandering around town, I feel it makes me look like a weirdo. A jacket is ok, if it's not too hot. But when it is hot, I'm out of options.
All this could be remedied with having fanny packs as an accepted accessory, making them less ugly and not tied to social dogmas and disrespect.
How I appear to the world is something that worries me all the time.