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.
Yeah, people tend to remember the product or service they see in the ads that makes them subconsciously choose that product for their own use. Come to think of it, I used a lot of services I have seen here on the forum just because I see them on people's signatures and avatar.