like pokewatt said they just want to show off their Pokemon, but some people that go to gts negogations sometimes see a level 1reshiram, kyurem, or zekrom, and probably don't know that they have to be hacked to be at that level. Also negogations will tell the trainer "there is something wrong with the other trainer's Pokemon. This Pokemon can't be traded." That could cause a person try to trade a legendary at level 9 and under at gts (not negogations)