I'd be surprised if there's a large number of people who bought a D&D book "absolutely cold" -- that is, having heard *nothing* about the game, found it on the shelf, and were intrigued enough to buy it. (Then again, I could be wrong...)
But, I don't think that's different from any other hobby. I doubt many people get into coin collecting, needlework, model rocketry, etc. just by stumbling onto it on a store shelf. Reading about it, seeing a demo, word of mouth, are all going to be much stronger, more reliable ways into the hobby. (That, and low cost-of-entry starter materials....)