Replying to Different doubles

In slopestyle comps these days I feel like I see a lot of the same tricks, even pretty similar grabs. Hung out and watched all of grand prix last week and couldn't figure out why people aren't mixing it up a little more (albeit conditions were awful, but I feel that way about most competitions). Off the top of my head, I rarely or haven't seen dub cork 7, dub cork 9, kang 9, kang 10, or butter tricks in comp. These have all been done and don't need enormous jumps like triple corks do. Thoughts on why these tricks or others you have noticed aren't done in comps? Are they just too hard?