If food delivery services were presented to end users as some sort of bidding model, sure, but it's not. It's presented as simply as "you order food, food gets delivered to you". There's no ability to see how my order might be affected by how much I pay.

For the record, I never use food delivery services because the upcharge is absurd. If I want food delivery it'll be pizza and that's it. At least that's an honest transaction and I don't have to wonder when my food will arrive or how cold it might be.