It abuses both your legal department and the law firm to send an invitation to compete for work for which the firm is not a plausible contender. Your project team has to answer their questions, respond to their requests, keep track of the firm in the process, and eventually deliver the disappointing news.
The firm spins its wheels, some partner gets her hopes up, and eventually feels abused – “It was all a show, a rigged competition and we were strung along.” You are not doing them a favor or placating them.
I highlighted this point from humane and practical piece of advice from Robert Haig, Ed., Successful Partnering Between Inside and Outside Counsel(Thomson Reuters/West 2009 Supp.), Vol. 1, Chapter 5 at §5:12. Responses to RFPs are far from costless, on either side, and deserve judicious deployment.