This is only if you lack the ability to train your instincts. I cover my front brake on my motorcycle every time I'm in traffic. I cover my brake on quick singletrack so long as the trail isn't too bumpy to keep my from pulling the lever by mistake. If you're new to two wheels, then no, you won't want to cover your brakes. If you've trained yourself to only grab your brakes when your scared, but only get scared when you should grab your brakes, then you're good to go. Just like your survival reaction to look where you don't want to go when you get scared, this instinct can be trained.