>What's the mechanism that forces restaurants to partner with these food delivery services? Threat of competition if they don't?
The mechanism is the ubiquity of folks using "apps" instead of contacting restaurants directly.
It used to be in NYC that every time a restaurant made a delivery, they'd leave paper menus for the residents.
Now, you either go through an "app" (read: an inferior interface to a website) or a search engine to find restaurants.
Aside from the fact that a low/mid-priced restaurant likely doesn't have the tech expertise to set up an online ordering platform, or the financial resources to purchase a point-of-sale system that includes such functionality or to contract with a developer/hosting provider to do so, getting on these sites may seem to be the only way they can maintain their business.
And since GrubHub, et. al use SEO spam to get themselves at the top of search listings, have contracts that forbid restaurants from charging less if orders don't use them, and then take all the profit (and then some) from the bulk of transactions, the deck is stacked against such restaurants.
I suppose you could argue that if a restaurant can't compete in the market, it should fail. And most do. The average lifespan of a restaurant is just five years, and the vast majority fail within one year[0].
But those aren't the restaurants I'm talking about. I'm talking about neighborhood institutions that have been open for decades being forced to close because all their profit and then some is being taken by services like GrubHub that aren't even providing delivery services, just listing on their site (which runs from ~12-30% on every single order).
The insertion of the middle man here, taking up to a third of the revenue on every single order which provides just a listing service (they actually charge the customer for delivery service if the restaurant doesn't provide it -- not the norm here in NYC), has put many wonderful restaurants out of business.
This increases prices, reduces the diversity and choice of cuisine and quality, without providing any value, except in listings and credit card processing.
