Drivers can tell if you don’t tip and all of the experienced ones will decline your order.
Though these apps have done a lot of work to conceal the amount the driver actually gets until delivery is completed.
Americans need to remove the idea of tipping. It's archaic, because it was originally there for an aristocratic/wealthy patron to show off their status to the lowly servants of an establishment.
Just charge a price, and have it include the full service fee required for providing the service.
IMHO, this isn't a new phenomenon. Close to 18 years ago, I lived in a city with a popular pizza spot that was about a 10 minute walk away. Normally I'd walk, but having a newborn make that challenging, so I'd get delivery.
Typically, the delivery would take 60+ minutes on a busy night, but after a few consecutive Fridays of a decent tip for the order, the pizza would arrive "burn your fingers" in about 20 minutes.
Markets have prices.
Open markets have transparent pricing for efficient discovery.
Concealed prices in deniable auctions are closer to dark pools than open markets.
It doesn't help with situations where drivers are multi-apping (accepting orders across multiple apps and juggling them). The drivers don't even know you have priority.
edit: and in the US where you can definitely see the tip up front, you will almost always find that the order will get picked up quicker if you increase the tip by the equivalent of the priority fee. But you may well get stuck with a delivery before yours.
It's wild because this happens maybe 10-15% of the time for me when I don't choose priority, but it's around 80% when I do.
I ignore the option now and just bump the tip if I want a chance of better service.