Board Thread:Legitimate Canon Questions/@comment-13895380-20160319150733/@comment-26879545-20160321113401

Mostly because it's up to the actors on whether or not they want to return.

Some actors, like Colton, cut ties with the show and don't want to go back to it. They have their reasons for not wanting to return and it's their decision. They're not going to change it just because there are so many fans who loves the character they play.