Drivers for ride-sharing startup Uber Technologies Inc. have filed a suit in the Northern District of California, accusing the San Francisco-based company of skimming off tips and misclassifying them as contract workers. The case was brought on behalf of all drivers except those in Massachusetts.

Part of Uber's appeal lies in its simplicity, with a lift just a click away. Riders are billed automatically through an app, which emphasizes that the price charged is all-inclusive: No need to tip, because you already have.