Because Wobuffet's two main moves, Mirror Coat and Counter, can do heavy damage to most pokemon. He can take some heavy damage, and many uber pokemon, like Kyogre, Groudon, or Mewtwo are very easy to predict. Since they can't swtitch out, they can either use a support move (which isn't seen too often in Uber) or attack. Chandelure can't counter enemies like Wobuffet, and if anything, he'll probably be eaten alive seeing as almost anything in Uber can counter him. Wobbufet also has encore, which forces his opponents to use the same move repeatedly.