expects us to pay their wages and for our food.

well, yes. look, I'm not a fan of the exploitative "gig economy" either, but you are paying for two things that won't ever be offered for free to you: (1) food to be prepared for you, and (2) the service of someone to transport it on your behalf. for the prior you pay the menu price. for the latter you pay service fees and tips. if you don't want to pay extra (atop menu prices) to have someone bring you the food, don't ask someone to bring you food for money.

the scummy part is not that you're being made to pay for the services you're requesting, it's that the services sometimes lie about how the workers are being paid and how much the service actually costs by wrapping up the worker's base pay (essentially) as a "tip". yes. shitty.

but i'm not sure how this differs much from, say conventional non-gig "free" pizza delivery wherein the cost to the business of(poorly) paying drivers is recouped by elevated menu prices and there is still an expectation on the customer to tip the driver to make it sufficiently worthwhile for them.

if services are taking the tips for themselves when people assume it goes to the driver, that's bad. that's happened, yes. and fuck the service for doing it. bad pizza joints have done the same thing to drivers for years when they get credit card tips or tips online, too. that doesn't make the "conventional pizza delivery economy" as a whole evil, it just makes those unethical companies assholes that should be avoided.

Yes, and the solution is to pay the business their money but stiff the worker so he quits and the business can extort some other poor sap down on his luck, that'll teach those rich bastards who never knew the delivery guy existed to begin with! Definitely don't change your habits and instead cook, pick up, or only order from places that do pay fairly, because that would inconvenience you, and strong opinions are only fun if they burden someone innocent who isn't you!