Right now restaurants are in a damned if you do damned if you don't situation with the various delivery services out there.
If the restaurants explicitly agree to do business with grubhub and the like, they have to give the delivery service a 10% cut. The delivery service also takes a percentage cut on the customer side. I think there's the expectation that the restaurants keep charging the delivery service the same amount for food being delivered as they charge anyone who orders food from the restaurant and picks it up. This forces restaurants to raise the price for all their customers to pay for that 10% cut.
Have you noticed that the prices for food via delivery are higher than the price for food you pickup? That's not due to the restaurant charging the delivery service a discriminatory price, that's actually the third way that the food delivery service takes a cut.
Now, as a restaurant owner, you look at all these facts and decide that the delivery companies are fleecing you. You decide you'll use the waiters and waitresses you already had on staff to deliver the food to your customers, and you'll charge them something like $5 for delivery. Not really that unreasonable, given the circumstances, right?
Well, what happens in those cases is that the delivery companies will list the restaurant anyways. And they'll offer free delivery. And they'll charge less for your food online than you charge them. They take the financial hit so later they can come to the restaurant owner with the data to show that they really need the delivery service after all. They'll undercut your business to get a greater market share. They've got lots of VC money to burn, that you, as a restaurant owner, can't compete with.
Through all of this, customers will leave negative reviews on Yelp, for the restaurant, when the wrong food is delivered, or their food is cold, or their order was delivered to the wrong place. The reputation of the restaurant takes a hit due to the third party's shoddy delivery people.
That's what this law is attempting to address.