That part often isn't true. These companies frequently list restaurants with whom they have no relationship, and when a person makes an order on-line, they just send a driver with a credit card to purchase it takeout and pick it up. It sounds fine on first look, but the way it plays out, this causes huge brand management issues for the restaurants. Customers are charged more than they expect, not realizing delivery company is misrepresenting prices, and complain about delivery problems (which are frequent) to the restaurant, despite that restaurant having nothing to do with delivery, and often no knowledge of it. Sometimes there are even darker shenanigans happening. GrubHub replacing restaurant phone numbers with their own comes to mind.

All this is done to collect/encourage usage data, and then offer the restaurant a formal relationship, in a form of borderline extortion. And as owners of ever growing network/distribution channel, these companies can very much force businesses into accepting very unfavorable deals. They don't care if they're burning these restaurants to the ground, because there will always be more. They make money off the churn.

Don't get me wrong, I like being able to order from a wide variety of restaurants using the same, streamlined interface. But after learning how bad a deal these companies are to the restaurants, I steer away from those platforms. I don't like when multinational corporations are using their weight and dishonest tactics to crush the small entrepreneurs from the community I live in.