Short answer: because wedding buyers research locally and decide slowly, and a Jacksonville-specific listing reaches them during the months they are comparing, at a cost that does not reset every time someone clicks.
Wedding search is local by nature. Nobody plans a Jacksonville wedding by browsing national inspiration alone. At some point every couple searches "wedding venues Jacksonville FL," "waterfront venue Jacksonville," "outdoor venue near St. Augustine." That is a small, high-intent audience, and it lives in one city.
The research window is long. A couple books a venue nine to eighteen months out. Pay-per-click spends your budget on every early browse. A listing sits there for the whole window, at one annual cost, and is still there for next season's couples.
You are being compared, so give them something to compare. Photos, capacity, what is included, real reviews from local couples, and the neighborhood. Venues that fill their listing properly get contacted more, because the couple has already answered half their own questions.
Where the plans fit. Venues usually sit on Professional Services. Groups running multiple properties, or an established venue that wants to own the category in Jacksonville, go to Corporate for multiple locations and premium placement. See current plan prices.
What surprised me: the highest-value inquiries did not come from the ad slot. They came from a member seeing the venue three times in a month, once in the directory, once in Insider Choice, once as a deal, and treating it as the obvious local option.