I see the RFP process from the viewpoint of a buyer and a provider. From the buyer's standpoint, when we start a project we simply don't know what firms are capable of doing what we want done. The RFP gives us a level playing field to compare costs, capabilities, and experience.
Without an RFP, particularly for complex projects, you can spend months scoping out capbilities, refining your needs (both of which you should be doing AFTER you form a relationship.)
Which takes longer for a firm? Researching an RFP and presenting a document for a potential client's review or spending eight months going back and forth trying to figure out what to build. Of course, the latter. The difference is that providers get paid for those eight months (a plus for them) while buyers get nowhere.