I don't look at tips as part of the pay of the wait staff - that's between him and his boss. The tip is a gift. There's no reason I can find that a waiter should pay income taxes on my gift to them. My kids don't declare Grammy's $40 gifts or Pop-Pop's $50. I didn't declare my the value of my wedding gifts.
Tough $h!+ if the government wants a bite.
Legally, it isn’t a gift though. It is compensation. It is, in essence, commission that you control the rate of. No different than the commission you pay when you buy a car except that you control the rate.