<argument for free market>
Aside from the bad tippers, whining servers, and media whores trying to stoke the fires of controversy, it is wonderful how the market figures this stuff out sans state involvement. Everything is voluntary. All exchanges between restaurant owners, servers, and customers occur without the threat of violence.
No need for the state to mandate 15% tips across the board. No need for the state to require servers to become licensed to do their jobs. No need for regulation of any kind.
Tipping is customary in some locations (U.S., Israel, Croatia), and not in others. And for the most part, everyone gets along. No riots, no murders. Meanwhile, we (consumers) get to enjoy nearly any type of food we want within minutes for a low cost.
That is one of the gifts of a free market.
Imagine: five years from now, the state may mandate that servers are paid a wage of $10/hr. This will increase costs for restaurant owners, who in turn might increase menu prices, reduce service (fire servers), or eliminate menu options. Meanwhile, tips might become a thing of the past, removing an important tool customers use to reward good servers and provide feedback to bad ones. Increased prices, lower level of service, diminished options.
Those are among the "gifts" of the state.
</argument for free market>