Answer:
I am the fountain from which no one can drink. For many I am considered a necessary link. Like gold to all I am sought for, but my continued death brings wealth for all to want more.
Almost everyone needs it, asks for it, gives it. But almost nobody takes it.
What do you have when you're sitting down that you don't have when you're standing up?
Look into my face and I'm everybody. Scratch my back and I'm nobody.
They are many and one, they wave and they drum, Used to cover a state, they go with you everywhere.