I don't earn tips these days, but I think tip income should not be taxed, and here's why:
A tip is not legally required. It is a gift, a way for the customer to say "Thank you." Completely discretionary.
If a single person, say a close friend or family member, were to give you a cash gift of $18,000, that is not a taxable event to either the giver or recipient.*
However, if 18,000 people were to give you, a waitress, a cash gift of $1 each , all 18,000 cash gifts are taxable to the recipient.
Who tends to pass out gifts around $18,000? Rich people, that's who. Who tends to tip their servers? Everyone else.
Working class people have their gifts taxed. Rich folks, not so much.