There are two parts of the USA when it comes to tipping. There is NYC and there is everywhere else.

In NYC, you hand money to everyone within sight. In the rest of the country, it's much more rational.

But even in NYC, you wouldn't tip a concierge for something that doesn't require 'contacts.' The rule I follow is that there are no small concierge tips, the appropriate amount is either nothing (for almost everything, and certainly everything routine) or $20+ (for getting you something that you couldn't get on your own).