Saw the recent note about streamlining segments by only keeping the most popular ones, detecting and removing fake attempts, etc. That's great. That said, I would say that one reason why some people make duplicates is an attempt to make a better spatial representation of the route so that anyone taking shortcuts will not have their attempt registered. In making this update to segments, I highly recommend strava update the GPS match precision required for a segment to register.
As an example, take the Black Widow trail in San Diego, CA, black mountain area. The trail starts with a few switchbacks but there is also a steep hiking trail straight up the middle. Some bombers with their DH bikes send it straight down this trail, but their rides are registered into the segment with all the switchbacks. As a result all of the top attempts for the Black Widow trail are from DHers skipping all the switchbacks because the GPS registration is too forgiving. I am hoping a change could remedy this.