If DoorDash can’t be arsed to ask for permission from whoever to deliver, then maybe it’s for the better that they don’t deliver that place. Sure, it costs more than just adding the place to their site, but the restaurant is having their image harmed by soggy food. If that restaurant doesn’t want to allow delivery, they should have that option.
It's bad for the restaurant to be harmed this way, of course. But it's not a choice between "do nothing" and "force them to ask permission". Under this law, a restaurant might refuse permission for other reasons. And some of those reasons would be bad for consumers. If a similar rule was applied to non-food items, it could be a very harmful blow to the first sale doctrine.
A restaurant is already allowed to refuse to sell arbitrarily. They have the right to freedom of association, just like anybody else, with narrow exceptions when it's targeted at protected classes. And restaurants are already allowed to do all sorts of things may depart from the gospel of revenue maximization.
This is the sort of thing we expect to be taken care of by the free market. If signing up with a delivery service is truly in their interest and aligns with what they want their business to be, they mostly will. And if not, that's fine.
Bad reasons are a dime a dozen. Maybe they just don't want to. They don't like the idea, and they're stubborn. Or they made a deal with one or two companies and don't want to allow others, even though some customer would really prefer the disallowed ones or can't get service from the allowed ones.
For bad effects, it means that the customer can't get the food they want, even with 100% knowledge that it's a third party picking it up, and that the quality will be imperfect in a way that's not the restaurant's fault.
Here, let me quote someone else from this same comment page: "Last night I wanted w bottle of alcohol for new years celebration. I already had a few drinks so I didn't want to drive. Unfortunately no delivery service had an agreement with any local liquor stores."
And, I mean, for non-food items imagine how bad it would be if you needed explicit permission from the manufacturer to sell something on ebay. Food's not that different.