[mikeash]

It's really just a matter of whether it's customary, which is only loosely related to whether it actually makes any sense.

Your taxi driver gets most if not all of your fare, but it's still expected to tip them. A grocery store cashier gets none of your payment directly, but you don't tip them. Don't try to make sense of it, just do what others do.

[ghaff]

Then there are a fair number of cases where reasonable people disagree. Maid at hotel, others at hotels/parking attendants/etc., Uber/Lyft, the subject of this article, limo driver, bartender (in a bar or at an event), and so forth. You can tip in all those situations but I'd argue it's not the strong expectation that tipping at a sit-down restaurant is.

[behringer]

If you don't tip your bartender you won't get drinks very long!