For those of you who might not have a sense of history going back this far, there's an old documentary from 2001 called
e-Dreams, and it's all about this former Goldman Sachs guy who wanted to get into the dot com boom by starting a delivery service in NYC (which expanded way faster than it should have), and they'd either pull stuff from their local warehouse or go somewhere to buy what you ordered and then deliver it to you via bike messenger. If you ask me how in the holy hell this was considered a strictly internet business I couldn't give you a good answer, but my point is that what all of the current delivery services are doing isn't a new concept at all. The business that does the delivering just jacks up the price of whatever it is your torpid ass can't get up and get yourself.
And there are plenty of businesses that do their own delivery. But either the cost of the service is already baked into what they charge or they do it as a very nice customer relations feature (like my local mom-and-pop pharmacy, for instance).
Let's say you want to order from KFC, Subway, McDonald, Pizza Hut and Starbucks at the same time, will you choose to use ubereats or 5 applications from each restaurant?
Um. That scenario could only apply to a minute percentage of any food-ordering population at any given time, and I'm picturing somebody who can't fit through a door frame ordering food from all of those places at once. You never know what someone like that would prefer.
Back in the real world, people who don't have money to waste on middle-man delivery services are probably going to just order from some restaurant that does deliver, like Domino's or the like. They're still not super cheap, but the alternatives are highway robbery IMO.