For me, the tip isn't about what the server makes as the base pay. I really could not care less. I tip because tipping gets me better service. Particularly someplace I will return. (I call it pro-active tipping).
When I worked for a German company and spent several weeks a year there, or in Manchester, England I found the service - lacking. I got my food, and it was what I ordered. But, that is really all. Until I talked to my boss and got permission to tip 15%. I suddenly got truly excellent service.
So, with take-out orders, is there a chance for the waiter to do better than average service? No. So, I tip enough to make them not lose money.
At a fast food place, there really isn't a chance to shine. So, no tip.
Bartenders get tips so I can get their attention for a second drink.
Anyone cutting my hair gets a tip, because I really care about my hair.