With a website that has a table reservation system you don't have to get interrupted by the phone all the fucking time by people when you're trying to chop onions or set tables.
Dine-in restaurants that are on the fancier side sometimes have that. I know US is phone call adverse but phone call appointments and bookings via talking to a real person rule here. Austria is very old school both in terms of service offerings and in consumer behavior (cash based, tech adverse, etc)
Ordering apps handle that nowadays, it seems routine for restaurants have have multiple apps on multiple devices as their intake.