Bogging down a movie with "canon" and TV show background isn't going to help. It could be said the TNG-through-to-Nemesis "universe" was being dragged down by its own canon and history. Hence, reboot with the new movie and bang, success.
Yes, Khan had a show origin "backstory," but that was explained and done with with a short little "speech" by Khan. It didn't drag the movie down.
Trying to tie in and bring in so many elements from the series is just going to appeal to hard-core fans, who aren't a big enough audience to make a movie successful.