The idea is that the sound of an impact drill adds to the noise pollution of a supposedly "natural" area, and that they're "too easy" so they result in a proliferation of bolts in the rock. There's a lot of argument back and forth on the subject in places like Yosemite, where it sees so much traffic that it could hardly be called natural anymore. Personally, I'd rather hear 12 seconds of a Li-ion rotohammer than 30 minutes of some dude whacking a hand drill with a hammer, and since they make better holes, a rotohammer drills more symmetrical holes and is going to let the bolt seat better and it won't result in a proliferation of cratered out rock where old bolts pull out and have to be replaced by drilling new holes next to it. It's a touchy subject for a lot of folks. Some don't like "permanent" protection at all, but in places they don't allow bolts you end up with "temporary permanent" nylon slings tied around rocks all over the place. Doesn't really seem better.
