Restaurants generally have low margins. What brand recognition do social media platforms have with an average person? How much does it cost a restaurant to list themselves on social media? That's your competition, widely-known and free.

You'd probably have better luck if you gave them an actual dotcom address, and you managed all of their online presence for them (Google Maps, Facebook, Instagram, etc.). But even then it's hard to compete with free, especially when your prospective customers are stingy.

Edit: I suppose you're also competing with Uber Eats. You can already see menus there, whether you want delivery or not.