I have never used those services before because I would be afraid to allow anyone other than a family member or friend bringing food to me. Who knows what they might do to the food (or what they might sample) in their car between the store and my house? The only time we ever had food delivery to our house was when our daughter was the one who was the delivery driver!
You saw the same slideshow I did, right? The one about what happens to your food between the order and the delivery by the driver?
Nope - didn't see it. But I have heard people talking about it in general. I actually listened to a podcast recently (wish I could remember who and when) where they were debating over what was "acceptable". They were doing a comedy bit and it was all tongue in cheek, but they were talking about how it was okay for the delivery driver to take a french fry or two, but not okay to take a bite out of a sandwich. Somewhere in the middle was the question of whether you can take a chicken nugget or mozzarella stick or a sip of soda.
The justification was that fries are obviously not individually counted and you aren't necessarily contaminating them all by carefully taking one or two while not touching the others. The fry box is still full. A drink's volume is not significantly altered if you take a small sip, but if that sip involves a straw that is intended for someone else - you are contaminating that straw if you use it. Chicken nuggets are specifically counted, so even if you can take one without contaminating the others, in doing so you are making a more definite impact on the volume of the food order. Taking an actual bite out of a sandwich both contaminates the sandwich and impacts the food volume and is generally a disgusting thing to do to someone else's sandwich.
So it's a full spectrum there!