I'm not really clear what you're asking. I think you mean to say some thing like "some companies have research departments. They research things like marketing, business intelligence etc but they don't have a dedicated team for usability research. Why don't companies have a usability research department?"
Well, competently run, large companies do have dedicated UX teams along side marketing and business etc. Sure there is lots of cross over but if there is good enough internal communication this overlap is good .