Someone posted above about how tipping allows a waiter to somewhat control his/her wages. This is true. I did it all when living in Knoxville. I waited, was in charge of our banquet room/parties, delivered for parties of 50, 100+, worked the to go window, etc... The few times in which tip-sharing was required, the hard workers like myself worked just as hard; the lazy asses were, well, lazy.
All the arguing on this thread somewhat simplifies the point. For example, it's possible this guy just put the sandwiches in a bag and took them to another location. In that case, he'd better be really effing happy with $87. When I catered for the Mexican restaurant I worked for, I went in 2 hours early, organized everything, made tortillas, etc... I then set the food up at the location and returned later to pick up the serving chafers, utensils, etc... So I often put in a good 3+ hours on orders over $500. I almost always got 25%+. There were other orders in which I basically just took the food (in disposable containers) to another location. In that case, $10-$20 was ok assuming I didn't have to drive too far.
As far as to go (Macaroni Grille), a buck or two for small orders/$5+ for orders over $50 was the norm.
One last thing... You never truly know the situation your waiter, delivery driver, etc... has "behind the scenes". Some places do share-tip. When I worked to go, I busted my ass all night helping others. It wasn't just a sit-and-occasionally put an order together. I had to help bus, run food, clean, etc... If it was a slow night and I only had a couple of orders, I worked my butt off for several hours for less than, say, $10. Customers would have had no idea. This is why I ALWAYS tip very well regardless of the situation. Hell, I'll tip well for bad service. The only time I ever tipped as low as 15% was a time when the waitress - literally - sat on her phone at another table throughout our entire meal. Even then, I told myself that, perhaps she was dealing was something important.
tl;dr - There are many, many different factors at play when dealing with waiters and delivery drivers.