Perhaps because a lot more of them will be running around freelance industrial concerns than models of, for example, Huntley and Palmers' Biscuit factory or the Manchester Ship Canal system.
That's the reason I ordered Dodo. I am not sure yet what I am going to use it on but I do know it won't be a model of either of those two concerns. If I build a freelance industrial layout, or scene on a bigger layout, I think it would be more convincing to portray that industry as J Smith and Sons Ltd, Westwood Engineering Works or Hogwarts Brewery than to try and pass them off as branch operations of Huntley and Palmers, the MSC or any of the other original owners of W4s.
I imagine many prospective purchasers would welcome a selectional of fictional, but plausible, liveries rather than have Dodo popping up on every industrial layout throughout the land.