Personally, I think that it is one accessory that I can do without.
Okay it can be a nightmare to go out with the girlfriend when she doesn't want to take a handbag, " I might lose it or get it Pinched, can you put my lipgloss/purse/keys/mobile in your pockets, please", but those over the shoulder bags are lot more practical and to be perfectly frank, alot less effeminate than a "Manbag".
I think he is a bit of a fashion victim.