My answer in no way disagrees with anyone who states that this arrangement is illegal, that the best course of action is to not patronize the establishment, or that tipping is not required. These are all entirely true.
After personally knowing one waiter who works (perhaps illegally as he may not be permitted to work) in a particular restaurant...
(Emphasis mine.)
Sorry for your friend's situation. It sounds unpleasant.
If he is not permitted to work but does, he is breaking the law. The employer is breaking the law by employing him illegally. It should come as a surprise to no one that an employer who breaks one employment law, breaks another also.
All of that aside, while tipping is not required, it is extremely poor form not to tip when receiving sit-down service at a restaurant in the US. There are as many opinions about this as there are people, but if you're asking for societal norms, if you can afford it, 15% is the minimum.
Handing the tip directly to your server is generally pointless. Many establishments have tip pools or tip-sharing arrangements, where some of the people who you didn't interact with directly, but are still involved in your service (bussers, expo, bartenders, etc.), receive a portion of the collective pool. These schemes also often serve as normalization, so no one server benefits disproportionately from better or worse luck. I have no idea if these schemes are legal, but from my experience in the industry, they are normal.
I understand that the main point of tipping in restaurants is to supplement low wages for service staff.
As an American with experience in the service industry as a server and as a manager, I would disagree with this. This is a common complaint but it is factually incorrect.
The federal minimum wage stands, even if a server's posted hourly is below it. Servers declare their tips.
If the amount earned hourly, between wages and tips combined, is below the minimum wage, the employer must pay the difference.
I do not know how many employers either ignore this or get this wrong. I've worked at several restaurants in different states, and every single one I've worked for does follow this. Most have made mistakes that I've caught but none have ever disputed a correction.
This does come with two provisions:
- The actual (legal) minimum wage isn't the putative minimum wage right now. McDonalds (they're often considered a hire-all entry job) in my area pays $13 an hour while the minimum wage is around $8. This is a big difference and I'm not taking a side. It's the way we do things in America.
- Servers routinely lie about their tips when reporting for accounting and taxation, in my experience. I've met some who do some mental math to put their declared tips right in the minimum wage area. I've also met many who don't really care. I've also (as a manager) been instructed to dismiss a server who routinely declared such low tips that their salary had to be padded by the establishment. This person was under-reporting their tips. Lying on reported tips is tax fraud and is illegal. Then again, a lot of people break other laws routinely, like speed limits. Once again, I am making no endorsement of either side.
... I learned that he received a fixed daily salary and whatever tip the customers leave go to the owner of the restaurant.
(Emphasis mine.)
Is the fixed daily salary at or above minimum wage? I am not a lawyer but I don't believe that this is illegal in any way if it meets minimum wage requirements.
If the fixed daily salary is below minimum wage, this is definitely illegal.
So what do I do?
Try to help your friend get out of the situation. This requires somehow getting him on the right side of employment law so he can get a legal job where this is less likely to happen.
If you have presumed incorrectly and your friend is legally employed, or after he has gained the right to work, help him get a better job.
Until then, tip 15%. You're asking in Travel.SE so I presume you're not from the US. This is how we do it here. You are not breaking the law to do otherwise but you will be violating the social contract that Americans follow.
There are a great many Americans who have violated various social contracts (and laws) with mixed success. Martin Luther King, Jr. comes to mind, as well as many others. As a traveler, do you want to be in that company?
I know that I don't want to be an outlier, and definitely not a crusader, when I travel anywhere else. I can barely affect US laws as a US citizen. I feel like I am generally powerless to question, much less dispute, any situation when outside the US, whether societally incorrect or illegal, when I travel.