I'm not really angry about it, but I don't get it either, if we're already using Steam, it doesn't make much sense.
It's a free service that will allow you to completely integrate your mod in the game. If you don't like it, don't use it (upload it to your servers or a different host).
May not be a big deal but it does seem odd that with all the Steam integration and bindings that you'd need yet another 3rd party tool involved.