well they should, because their own store doesn't even work. Ubisoft notifications and their store both have problems and have it looks like for well into a year without resolve so maybe going back to Steam store wouldn't be a bad idea. Least it works.
Why should Ubisoft waste resources and also pay to that steam leach for the content?
Ubisoft does not care any more about steam. They no longer releasing they new games on it either.