I believe tipping is primarily cultural default and companies using human psychology to guilt them into it. Most Americans worked at restaurants while attending college. They are conditioned to think its perfectly acceptable for an employer to pay $2.13/hour and customers must pay tips to support them. This became a cultural default. There is another cultural phenomenon, people mostly go out on dates to restaurants, usually the man foots the bill, and wants the woman not to think of him as a cheap person.
All checkout systems now ask for a tip, and another asking to donate to their own charity (Ronald McDonald House Charities or some other garbage charity), guilting the buyer into giving a tip and/charity for the billionaires 'non-profit'. We foot the bill for the billionaires generosity and kindness, they will go give TED talks on how awesome they are.
CVS was sued for using customer donations at checkout to fund a corporate philanthropy pledge: https://qz.com/cvs-customer-checkout-register-donations-laws...
To be clear, I was listing examples of traditionally tipped jobs. That wasn't comprehensive.
The bellhop/valet is just standing around waiting for some chance to perform a free service in hopes that maybe he can get a tip. He’s likely near minimum wage for his time and tips are an expected to actually make it a worthwhile activity. That said, I don’t carry cash often enough and regularly don’t tip these services any more. I try to avoid using them if I can’t tip. Sometimes that’s not an option, like a restaurant that only has valet and no nearby parking alternatives. In those cases, I let them work it out with the restaurant.
The apps and preset percentages are generally seen as a greed signal. If they offer 25%/30%/35% as recommended options, I’m likely to just leave a $5, $10 or maybe $20 tip even if the bill is huge. But it’s usually a lower percentage than if they just allow me to click a 15% button.
These apps also regularly add tip to the post tax subtotal which is another reason I usually just use the $5/$10/$20 amounts commonly these days. No matter what I spend, I have a hard time ever rationalizing more than a $20 tip. A waitstaff serving my family at a nice restaurant doesn’t make sense to tip 25% of a $500 bill. Their service is never that valuable to me. I like the idea of living wages but I also think these jobs are sort of, or should be, some of the lowest paying in the economy. People working them like a career and raising a family on that income doesn’t make sense.
Also, probably an unpopular opinion, but if there’s any extra fees added it comes out of their tip. Like I commonly see a “mgmt fee” or “service fee” of 3-5%, it’s never known until you are seated and read fine print on menu. At that point I’m already pretty captive and probably already know what I want to order. It just feels sleezy and dishonest as a business practice so I leave bad tips and a note why on the bill.
Overall, I wish tipping would go away and just have menu prices.
I will not tip at a drive-through oil change service.
I will not tip at a fast food counter.
I certainly will not tip at a convenience store.
Every single new tipping situation is a company begging me to subsidize their employees' wages instead of increasing them. Screw that. I'm not participating, and they can't make me. Those existing jobs were grandfathered in: waiters make below minimum wage on the expectation they'll make it up in tips, and that's f'ed up, but I can't change that by myself and I'm not going to stiff someone making sub-minimum to prove a point. All the others? Those cheapskate bosses can get bent. Pay more if you want to keep good help. Don't literally beg me to donate money to your employees as a charity.