I'm seriously wondering...Why are most mountain bike bars so wide? Yes, wide is comfortable and wide opens the chest enhancing breathing, but it seems to me that if you're trail riding, they could hook into bushes, branches or other growth on narrow trails making them unnecessarily dangerous.
Where I live, the growth isn't close in enough to catch on the bars. Wider bars provide better leverage to increase confidence, and enable shorter stems. Shorter stems handle better in loose sand and gravel, reducing the chance of going over the bars. Plus there is the cool factor.