When a small team encounters a much larger enemy, they execute a breaking-contact maneuver.
only costs a few dollars per weapon to add that capability to the rifle. Just doing a cost/benefit analysis will tell you that dramatically enhancing the capabilities of the rifle for such a small additional cost would always be worth it.
situations like CQB (close quarters battle, clearing rooms) where the distances are often just a few feet, don't require accuracy. They require half a dozen rounds pumped into the bad guy in a half a second, because you don't want to worry about if you hit him or not, if he's dead or just wounded, if he's wounded can he get up and shoot my friends or detonate a bomb vest because things are happening fast
Another reason is that under all the stress and fatigue of combat it's actually pretty damned hard to maintain the accuracy you achieve on the rifle range.