Yes but having one payment button doesn't mean the service needs to manage its own delivery.
Consider the example of Amazon marketplace. You still have one payment button and you can still shop for things from different vendors. Yet the order fulfillment can be done by Amazon or the seller directly.
If such an arrangement is possible on Amazon, it must mean that there are shops that trust their own fulfillment more than they do Amazon's. It is entirely possible that some restaurants will want to own that delivery experience as well.
Consider the example of Amazon marketplace. You still have one payment button and you can still shop for things from different vendors. Yet the order fulfillment can be done by Amazon or the seller directly.
If such an arrangement is possible on Amazon, it must mean that there are shops that trust their own fulfillment more than they do Amazon's. It is entirely possible that some restaurants will want to own that delivery experience as well.