Its all marketing
What property are you talking about?
I rarely use concierges, but on the few occasions I have used one for a recommendation, each time the concierge has given me a card from the restaurant they were recommending. The card entitleld me to something free, like and appetizer, desert or X% off the food portion of the bill.
I am sure restaurants near hotels call up concierges, the same way they do executive assistants, and invite them to tasting, events, etc..., so that the concierge/assistant can then recommend the restaurant to others.
Off the top of my head, this has happened to me in Cleveland, Chicago, New York, DC, Miami & Houston. In addition, my assistant and the Presidents assistant are always invited to restaurants for a "go see" as they books quite a few reservations.