I'm 22 and now I feel horror and disgust at myself because I knew most of those but a few surprised me

I absolutely hate having to pay for a product or service and then pay the person who helped me. But until things change, that’s the way it is. The person who is working those jobs shouldn’t get stiffed because we don’t like the way things are done here.

Tipping is not mandatory. Those employees go into those positions knowing how the pay is and that people don't have to tip. Find another position that doesn't mean depending on tips to survive. (pizza delivery driver experience here)

The pay structure is different in the US. A server in a full-service restaurant has a minimum wage of under 3$US. The federal minimum wage is 7.25$US. The server's tips are expected to make up the difference between those numbers; if they do not, legally speaking, the restaurant is obligated to make up the difference in the server's paycheck....but because there aren't much in the way of worker protections, a server who needs that may or may not get it, or if they do, may not be scheduled for additional shifts. The whole thing is basically that services cost less on the price board but in practice the difference is made up in tips. Think of it a little bit of how in most countries in Europe, the price of items on the store shelf will be inclusive of tax, whereas in the US, tax is calculated at the register--we know we're going to pay more than the listed price and we have a general idea of how much.

No, plenty of hairdressers simply rent the station from the owner of the salon. Normally you don't tip the business owner, who will usually also cut hair, but you should definitely tip the other personnel who directly provide services to you, whether they are stylists, hair washers, or manicurists.

And why should you always tip them? Most are paid decently well and are doing their job.