If you don’t want to tip at the places where tips are not traditionally expected, just say no. I have no problem bypassing that screen.
Making some guesses regarding the barista in the article, people aren’t tipping him much on average. If he’s making $400/month on tips, working 15-20 hrs/wk (guessing, since he’s also going to school) he’s getting $5-$7/hr in tips. I don’t frequent coffee places, but the few times I have been to one there is a lot of traffic. Considering he might be seeing twenty people per hour, the average customer is not being super generous. It’s more likely that the occasional customer tips very well and everyone else doesn’t tip.
Im on the receiving side of tips at my two summer j*bs: river guide for days trips and bike guide for multi-day trips. The company pays me by the day, so for river trips it works out to about $12-$15/hr and even less for the bike trips. These are both services where it is customary to tip your guides, but not everyone knows that. (Most cycling customers do tip but most rafting customers do not).
Even though I am not w*rking for the money, tips are great positive feedback. Our typical rafting setup is four guides working to get 100-120 customers down the river. We pool any tips and share equally, so if each guest tipped $1 (on a $65-$80 ticket) each guide would get an extra $25-$30 and we would feel appreciated. But that’s not what happens; sometimes we get $0, but typically a few groups tip us $20 each and we go home with an extra $5-$15 per guide. Let me be clear, I don’t need the money but it’s sad to get no tips.
TL/DR: A somewhat insignificant tip of $1 from a customer may have a big impact on the worker.