Tipping "tippable" employees is not a bribe. A social gaffe sometimes made by people who apply social standards from their home country when they travel elsewhere, e.g., the "Ugly American" in Europe.

At a high-end property, the concierge does not expect anything for routine services. But, if he pulls off a table at the sold out restaurant, the tickets to the sold out event and so on, those are "chits" which he can't replicate and they are invaluable.

In the US, we take care of the concierge, just as in England they bring cakes with the tea.