DoorDash and Postmates would deliver from every restaurant, whether or not they had a relationship with that restaurant. This helped them grow quickly. A DoorDash competitor that started today would not be able to grow that way because it is now illegal to deliver from a restaurant without the restaurant’s consent. DoorDash is already large and has a well known brand, so this doesn’t hurt them. It does hurt future competitors, for whom the cost of developing a relationship with every restaurant is cost prohibitive.
That makes sense, I see that point, but I think that stopping the bleeding is more important. Moreover the new set of rules can also benefit small competitors in the delivery space by allowing them to sign exclusive agreements with small businesses.
It may hurt future competitors but the law is still good because it protects the reputation of local businesses. This is like complaining that its illegal to pollute the local river. Or those arguments from backwards nations that they should be allowed to pollute like the western world did in the 1900s. Yes, that makes you money, but individual profits are rarely collectively beneficial.