I'm curious how many of you tip the concierge in the executive lounge?

Stayed at a Hilton this past week and saw some leaving cash on the desk, some spouting off their room number as they left (what is that about?), some just saying 'thank you' and some nothing at all.

Spouse was asked for our room number once.

Just curious about all of you out there and what your tipping policy is with the concierge. If you choose to tip, what do you tip and for what?

Jelliott