I like bars that are a bit narrower too. One of my buddies says that with wide bars it's like welcoming the wind with open arms...i.e. not very aero. Part of it is style/trend. Years ago bars were narrower. Nowadays, wide seems to be more common. With mtbs, it's gotten absurd, IMO. It's mainly a matter of personal preference so think about it, maybe try a few widths, and see what you like. Remember, when you're on the tops, the distance between your hands is a lot less than when you're on the hoods or in the drops. Does this cause you any issues?