Agreed, as a go-to guy in the office, I often feel the same way.

One thing I've noticed is that even if people don't actually interrupt me, the expectation that they might at any minute prevents me from fully concentrating on the task. Having some sign to indicate that for the next, say, 30m I should not be interrupted, and having people respect that, would probably help significantly.

On the other hand, the fact that people are constantly needing me is partially my fault, since there's stuff I could empower them to do by themselves with a little automation.