[gumby]

I almost never give my correct name for informal use (I am not a waiter, but for coffee orders and the like). Gives me a marginal amount of privacy (I mean, who cares) and makes it less likely my name will be mispronounced/misspelt with my coffee order.

If I were in a service job with a name tag I would definitely not use my real name.

[imwillofficial]

I take the opposite route, my name is everywhere. (See username) The wisdom of that choice however may be questioned freely.

[fy20]

I have a name that is easy to pronounce but hard to spell correctly, so it's easier to give a more common name, than making people struggle and explain how to spell it.