Some people like the hunt game involved in attaining the cosmetics. What other hunt do you have in this game? Rift after rift, greater rift after greater rift, and zero end-game. Just like how people collected the unique blues back in the day (and some still do), like the Murlocket, Rakanishu's Blade, Wirt's Original Leg, The Clipper, Griswold's Worn Edge, etc. Some people who play like to collect things, and cosmetics are things to collect. Besides, every player is different. You may not care but others do (obviously). Most importantly, it's none of your business what other players want to do.