To answer your first question: it's a better experience. Local restaurants have terrible websites with no photos and sketchy payment forms. Their delivery usually involves having cash for a tip. If there's a problem with your order, it's unlikely it'll be resolved.

With services like Deliveroo and others, your payment information is managed by a central third party, delivery quality is generally quite good, you get ETAs for your food, there's real customer support, the app/site is modern and easy to use with pictures and search, and you never need to keep cash on hand.

If every local restaurant had a system as effective as Domino's, I could see these services being in trouble. But that will almost certainly never be the case.