If you have worked in a restaurant, then you know. Most restaurants require waitrons (servers) to "tip out" busboys, bartenders, runners, hosts, and/or others involved in the chain of service. If you gain the reputation for stiffing the busboy, bartender, etc. (under-tipping), you will be punished by no water, wrong drink orders, forgotten bread for your table, etc. So, smart wait staff tips out correctly.
In California, though, there is a statute addressing the practice of "tip pooling." The primary purpose of the law is to prevent management from taking a dip into the tip pool, as it were.
Some folks believe that tips by law are retained only by the server who collects it, or who engages in "direct table service."
The Court of Appeal put that interpretation to rest in Budrow v. Dave and Buster's. There, a cocktail waiter objected to tipping out the bartender. No wonder he lasted a month, or three months as he argued.
Anyway, the opinion is here. I'll bet you some side work that the Justices themselves or the court staff pulled a few doubles in their day.