Tip is actually hardly related to quality of service. Michael Lynn's[1] research shows that people reveal their prejudices through tipping more than anything else. Being a young busty blonde female gets you way more in tips than being a middle aged black male, regardless of the actual quality of service.
In regards to that, I don't think tipping is a good system unless what you want is pushing discrimination in the workplace even further. Service should just be included in the price. But at least, the blind tipping model of these apps eliminates that bias. If you don't know who will deliver, you are less likely to tip the busty blonde girl more than the black man.
That's how it works for the most part on Grubhub/Seamless & Delivery.com (if it still exists). Seamless defaults to a 10% tip or $2, whichever is greater. Grubhub & delivery.com both asked the user to enter a tip amount or select a predetermined amount of 10, 15 or 20%.
I was a bike messenger doing food delivery for awhile. For the most part people tipped between 10-20%. The delivery person sees the tip in advance for the most part and can decide drop-off order based on that.
Additionally, most people who've told me their tipping practices for food delivery usually have a predetermined amount regardless of service/time/basket size.
I don't think the decision of which roles are tipped (vs paid a piecework/wage) ever had any actual incentive-aligning logic behind it.
Super Duper Burgers, for example, has zero table service, and you're expected to bus your tray. They still have tip jars and a tip field on the credit card slip.
Convenience stores now have tip jars too.
Don't try to reason with it, just follow established practice as best you can.
