100% of people in the U.S. know that tipping is a societal norm.
99% of people tip because because they know it is standard and it's the right thing to do.
Who said it was the right thing to do? 40 years ago, all these positions were not tipped. Who were the people who decided everyone under the sun should be tipped for doing their job?
The bottom line is, back in the 70 and before, most positions weren't tipped other than waitress and haircutter. Now all of a sudden, the movers, the cable guy is getting tipped.
My dad owned 3 lumberyards in the area. They cut the lumber to the customer's request, they loaded it in their truck, they did deliveries (yes they charged a delivery fee). They were in the heat, the cold, climbing up stacks of lumber, pulling out the good boards and there was never an expectation of tips. The drivers did not get paid extra, it was their job.
The fact is, we have been guilt ridden into tipping everyone. I don't use it as an excuse. I pay a service, I expect a good job. I do tip waiter/ess as they are under min. wage here. You all can hand your money here and there but I'm not going to. The very few times I have had pizza delivered, I did tip for their gas money.
The other 1% will resort to the thinnest of reasons to avoid parting with their money.
We all know tipping is expected for certain services. We all know we can avoid tipping by avoiding using those services. Waiter/ess are the only ones that I am aware that can be paid below min. wage therefore, that is the only one that should be expected.
Some folks want to have it both ways, "I expect you to serve me knowing full well a tip is expected, but you're not getting one from me.