I remember when "That sucks!" started becoming an everyday term. Wasn't that long ago. I found it slightly shocking, coming from the mouths of little kids. Not anymore, after hearing it hundreds of times.
I have to say, when I was a teen we started saying that, and my mother thought it quite improper and offensive. I will say that at the time I did not make the connection between the phrase and oral sex. It wasn't til some years later after having my own kids that I started thinking that really wasn't a polite thing to say...and I hadn't really considered it a "cuss" word.