So there's nothing wrong with takeout; during COVID you might buy it takeout, and eat it at a nearby table. Even outside of COVID, you might eat it in your car. This law is to ensure the restaurant has control over whether it's the customer taking it out (and it's then up to them how long they wait to eat it), or a third party (and the customer has no control over how long it waits before they eat it).

Because otherwise, there is nothing preventing Doordash or similar from adding the location to their app. The restaurant may not offer them favorable terms, or otherwise work with them, but even without official support, Doordash interopts with the restaurant's online ordering system for pickup (or even involves a human to call it in), sends a driver to pick it up ("Here to pick up an order for Steve"), and then delivers it. Nothing the restaurant can do to prevent it.

This restaurant is in a neighborhood. The reason they offer take-out at all was because neighbors just wanted to pick something up and eat at home. That's probably not 30 seconds, but it's way different than the amount of time a delivery company ads. It's also psychologically different if the consumer is the one in direct control of the delay.