Are virus threats (extremely) overrated?

Now this would make some up-front assumptions about being wise enough not to download/install unknown files, esp executables, and so on....but presuming one has a general clue, do they really buy you much of anything?

PS: I have one installed and running at all times as it doesn't degrade performance and nothing to lose. More curiosity than anything. I have heard some savvy I.T. people say they don't use one, to which I went :eek: