Yes, I know they say that "Captcha" is not needed because of their ...
Sorry, but Captcha is MUCH better than ANYTHING they can offer!
They either don't know how to add it or don't want to.
But, as you can see from the comments, we want it, so add it!
If they add an EASY captcha - I personally prefer they show 2 hand drawn numbers and ask us to add them. I hate Google's Captcha because every time I create a new account I have to guess 3 or more times.
If you add Captcha then this would be the PERFECT contact plugin!