The glass is the search. Somebody looking for good wine by the glass has decided not to commit to a bottle, and a bar that shows the current list answers that before anybody walks in.
Beginners want permission. Tastings, introductory evenings and flights are looked for by people who enjoy wine and feel unqualified to talk about it, and a welcoming tone converts them.
Occasions fill the diary. A date, a small celebration or somewhere to bring a visitor accounts for most bookings, and a page written for each of those lands in front of somebody comparing three addresses.
Enthusiasts search narrowly. A region, a grape or a particular style brings somebody who will travel, spend more and return, and who is invisible to a page that only says wine bar.