Nautilus got attention as being really solid and strong, and then nobody bothered playing him. I remember jungler from TD playing him in a tourney a few months ago, and now lots of people picking him up. There are so many champions now, and so many of them are still totally viable, that a legit reason for not seeing some of them is just "nobody has been playing them recently". Pros don't want to try and practice 13 champions all at once.
Also, silences stop channel ults. Startup to Fiddle's ult, Galio's Ult, Karth ult, Shen's ult, all stopped by silence.
--
http://img.imgcake.com/McBones/MvC3politicalupdatejpgyt.jpg