No, Smugmug does not "sell" or "promote" your site. Thus the weirdness of the original comment about "generate sales". Only YOU, the photographer, can generate sales. Same as if you hosted your own site, without it being under Smugmug.
Kevin is right in the post right before this. If YOU don't "sell" your site, and your pics, nobody gonna know to buy them, or even where to go to buy them.
All Smugmug is, is a web host in one sense. The benefit to them hosting, is all the photo printing, sizing, shipping, is handled by them, and not you. You are the only one that knows if all that is worth 15% of your profit. To me it is. All I do is post process, upload, and tell others where to go...so to speak
Ohhh, if anybody wants to try it, let me know. I can give you a referral code or something. If anybody is interested, I'll look it up and see what it is exactly and what it means to each of us.