When it comes to food, i tip and i tip well. Particularly if i intend to be back at said establishment.

Many reasons:

-) these people get paid like shit. I like to think: what if it was me? I still remember earning $3.50 an hour on my first job, and then taking home about $3 on my first day that i got from tips. And I was ecstatic, as it was the first money i'd ever earned.
-) I'm going to ingest whatever they are bringing me. Many adventures can happen from the kitchen to my table.
-) if i bring someone else along next time i'll be impressing them, skip the line, get the best seat in the house, freebies, etc: a lot of the little things will go my way if the waitresses are genuinely happy to see me.
-) I generally dislike being a miser. If i can't afford to tip, then i go to the grocery store and get my goods to make my own food.

That said, if the food is delicious, fresh, and prepared within three minutes of me hanging up and showing up to get it, of course i'm tipping on takeouts as well. It's a way of me telling the chef, " good job man" even though he will never see this money.