Imagine a plain white van. You add your firm's logo to it, but no contact details - no address, no phone number, no email address, no website. Would it be easy for would-be consumers to find you? Probably not. If, however, there was the logo, say Pearson, and a .com, to create Pearson.com, then the potential customers would know where to find you easily and quickly. So it's about access as well as helping to reduce costs by directing more people to your website where they'll hopefully book instead of phoning up (so they'd require fewer telesales people).
"Everyone writing for the Telegraph knows that the way to grab eyeballs is with Ryanair and/or sex."