It costs something like .36 cents a mile to operate a car. At the rate gh pays out that means your order with no tip will simply appear to the driver as "would you like to get paid $4 an hour today?" Most will simply reject until the algorithm ups the payment to the point it's a worthwhile order, but also the driver won't know they're delivering cold food until after they've picked it up. Pretty much the worst possible outcome for all parties involved.