As long as Steam support isn't cut, there isn't an issue for them or any other customers, and this does make sense from a business standpoint.
It gives them a direct outlet to sell to gamers that does not have any middleman, meaning they get 100% of the profits per purchase. If, for some reason, a player really wanted to make sure Ubisoft gets 100% of the money from their purchase, they now have an outlet to do that.
That said, I'll still be buying my games off of Steam. Also I wont buy anything with extremely restrictive DRM, which Ubisoft has up the nose, so I wont be buying their games regardless. (And yes, while Steam itself is a form of DRM, it doesn't hinder me from doing much, and I get a ton of services and other benefits to counter-balance it)