A standalone restaurant app is a hard sell unless it does something a website or phone call can't — but reservation booking combined with a loyalty program gives regular customers an actual reason to keep the app installed rather than deleting it after one use.
The reservation flow needs to show real table availability by time slot, send automatic confirmation and reminder notifications, and let a regular customer rebook a favorite table in a couple of taps — the convenience has to be immediately obvious compared to calling.
Loyalty tied to the same app — points for repeat visits, a free item after a certain spend threshold — gives casual customers a reason to become regulars, and gives the restaurant first-party data on visit frequency and preferences that a generic delivery app never shares back.
For most independent restaurants, this only makes sense past a certain size — a single small restaurant is usually better served by a strong booking page on its website; the dedicated app earns its keep once there's a loyal customer base large enough to justify ongoing engagement features.