I know that some of the viewers would like for Tofuu and Poke to join also, but I'm going to give out my thoughts and opinion as to why they might not join the SMP server.
First, is Poke and Tofuu. Their situation is fairly easy to explain. They have known the Cube for a very long time and to an extent they knew some of them before the Cube was even born such as H, Tybzi, and Grape. Let me take you guys to a little history lesson. During the summer of 2013 Poke, Tofuu, H, Tybzi, Grape, and later Straub were part of another SMP server called Vimcraft. The series did not last long for a few of them and was later discontinued due to unknown reasons. My theory is the lact of views or the lact of motivation to continue playing in the same server. I'm guessing the breakup was so bad that some refused to joing another SMP, but Straub, H, and Tybzi joined after maybe 5-6 months from joining any SMP servers. Thus the Cube was born. Fast forward to a few months, maybe early 2014. Tofuu, Poke, and a few others created a new SMP called The Surge or Surge or something like that. Long story short, it ended pretty bad as some of the members decided to leave in less than a month of the servers birth. I don't know what Poke and Tofuu are thinking, but I believe that after a lot of drama and past experiences from SMP servers they decided to take a break from it. I think they're mainly avoiding the drama that begin once they join or they're scared to join due to the reaction the fandom will create. Or maybe it's the fact that they're afraid that the Cube will disband just like the other SMPs they have previously joined.
If you knew all of this info than you are a dedicated fan and viewer to the Cube group and their UHC roster.
Again some of these are just theories. If you read all of these then congrats, you really deserve a cookie. *Hands over a oreo virtually*