These days everyone from your drug dealer to the local street corner panhandler ask for tips. The excuse seems to be that the machine "does that by default" and "management won't let us change it". Of course, as always, this only applies to North America (minus Mexico) and touristy parts of other select few countries who have been unfortunate enough to fall prey to this backwards American custom.
A tip is an optional payment for an especially well performed service from a service industry standpoint. I only tip for the following services, as this is how the custom was explained to me and drilled into my head when I first set foot on this continent:
A A waiter or waitress brings a meal to my table and looks after me while I eat my meal, including re-filling my water and being timely.
B A delivery person delivers my food to my doorstep
C A haircut person cuts my hair and chit chats pleasantries with me if I choose to engage in them.
D A bartender serves me a beer or another drink at a bar.
E A taxi driver drives me from point A to point B.
F A woman undresses on stage
My standard tip for A is 18-22%, before tax, for B 10-15% before tax, for C 10-20% before tax, for D $2-$3 for the first drink and 15% before tax afterwards, for E 10% before tax. F gets a reasonable amount dollar bills of course. This all depends on the quality of the service and how good everything goes. I have been known to step outside of these arbitrary ranges, but don't think there's ever been a case where I haven't tipped anything at all for A. Also keep in mind that where I live our waitstaff make the exact same amount as all other minimum wage jobs - there is no special lower wage such as in American states where they make $3/hr or some similar absurd amount.
I do not tip for pickup service since there is no service industry type service performed. Unless I get a previously agreed upon warm reacharound as part of my food order, there will be no tip. Why would there be? I will not be told what to do by a machine with no emotions or free will. We all know what tipping etiquette is, why are we being swayed by cheap business owners who can't be bothered to pay their employees a living wage?
And why do Americans think it's perfectly reasonable etiquette to tip 20% by default whether the employee behind the service makes $3 an hour or $15 an hour? Surely tipping standards in states where service staff make barely anything should be a lot higher than something like California. If your default tip is 20% in California, shouldn't it be 50-60% in Mississippi, where the poor wait staff make a measly $2.15 an hour? Is that even right?? The internet tells me it's right, but I refuse to believe it. Assuming it's right, how do these tipping standards make any sense whatsoever? Heck, even if someone is making $5 an hour, if you tip 20% in Cali, you should be tipping that $5/hr earner at least 40%. And why are we talking percentages anyway and not set dollar amounts? None of this makes any sense.. yet people will tell you with a straight face that it does.
I make an exception for locally owned businesses that I frequent on a somewhat regular basis. I figure I can spare to throw them a couple bucks here and there in order to support them beyond what is expected. And if I take a liking to you and we end up having good chemistry and I enjoy our time together enough, your tip % might very well go up.
Another trick the man has been playing on us is presenting these "tipping suggestions" on the post-tax amount. Tipping should be done on the pre-tax amount. Here in Ontario, Canada, we pay a 13% sales tax. If your bill comes to $50 before tax and you want to tip 20%, your grand total should come out to $66.5. However, the machine will tell you that a 20% tip would lead to you paying a total of $67.8. In this scenario, instead of tipping 20%, you are actually tipping closer to 21.6%. If you actually wanted to tip 20%, you'd have entered some % between 18 and 19. It might not seem like a huge difference, but many people have minute tipping standards, where a 22% tip is a job very well done, while 20% is a job done reasonably enough, and 18% is something slightly worse than that.
In the end, no, you shouldn't be tipping for picking up your own food, unless you really want to because you have some special relationship with the establishment (i.e. it's a locally owned store you visit once a week) but many people will, because they have weak wills and are easier to manipulate.