That's why I always order from places that have their delivery drivers and if that's not the case I'll just pick it up myself.
I was tempted to use one of those services recently but I backed out because I didn't trust the potential driver. I've heard cases of delivery drivers stealing the food, eating some of the food, or tampering with people's orders.
I don't know how people trust these drivers delivering them their food especially if that order is coming with a drink that comes with a lid that can easily be opened and tampered with...you don't know if they spit or cough up in your drink.