I think the problem is: what they call a "Tip" is more like a "Bid"/"Offer". People see "Tip" and thus believe its optional, I mean it technically is optional, but the base pay is like $2.50 so its customarily required. I think for even the shortest delivery of a place 10 minutes away with a 2 mile distance is supposed to tip at least $5. and if the delivery is done in 30 minutes, that's an effective wage of $15/hour, that is, if they get orders back-to-back.
Customers don't understand how this works and puts $0 as the "Tip", buts its really a "Bid", effectively making anyone who is willing to accept the order, to work below minimum wage. And also new drivers doesn't understand how this works and acceepts orders without a good enough "Bid", effectively working below minimum wage.
I mean, why even call it a "Tip" if its customarily required, just change the base pay to $7.50 (which I'm sure those companies will charge the customer for it, but anyways...). So for an order that takes 30 minutes, its an effective wage of $15/hour, assuming they get orders back-to-back. Much less confusion amongst both customers and drivers.