They can be, of course.

I worked in a food delivery company of the Just Eat group ~5 years ago, for 1.5 years. They take a comission of ~12% of the order price just by providing the platform to place orders. The technology is simple, then you have a sales team to acquire restaurants as partners and a customer service team to support when orders get lost or to update the menus.

Yes, there can be cut-throat competition in a market where a lot of money is sunk into marketing and the business is operating at a loss. But there are also consolidated markets where one platform captures >80% of all online orders and generates endless profits.

Just because a few VC-backed companies burn their many millions in a short time doesn't mean that there aren't large and very profitable food delivery services.

I feel like that is a pretty big stretch.

Basically there is a "cash cow" if someone can monopolize the market, not have competition, and if people are willing to pay more.

What isn't a cash cow under those circumstances?