It's a modernization of an already-proven business model. Chinese food and pizza was orderable by phone, and delivered for free or a small fee, 30 years ago.
So, the pizza restaurants proved that there's enough margin in a 25$ pizza to pay a minimum wage driver to drive it to your house. Delivery platforms come in and break this up: instead of the restaurant having someone on payroll to deliver orders, you just outsource that to another party (and pay them a fee, which is passed-through to the customer, and replaces money you would've paid the on-staff driver otherwise).
Why can't the food delivery companies provide delivery services for basically the same total cost as before, and subsist on extracting a small percentage of the value, which is freed up by the massive economy of scale that they can create by aggregating orders from several restaurants into a single pool?
Ditto for Uber... it's possible to operate a taxi company profitably, and has been for a hundred years. Shouldn't Uber have basically the same economics / cost per mile as a traditional taxi company, except be more efficient thanks to top-notch demand prediction that no local taxi company could ever build?