I really wonder this. I never clicked a signature ad and am wondering if it works for gambling sites. I need to be enlightened in this topic, because it looks like a waste of money to me.
Believe me, they are working just fine, even better than some people might expect.
You don't need to click every signature. It is enough that you see them, that way you'll learn name of the service sig is promoting.
From my experience I can tell you: I discussed many times new or interesting service I found via signatures.
I learned about many casinos, promotions, ICO project or services that way. The mere fact that they are around is enough.