I think the referrals have up to 90 or 180 days to actually convert, do they not? So be patient... good things ($$) come to those who wait! I'm just impressed that you have 21 referals. I have maybe 3
The only site I have where such things stand a chance have an audience which will probably never use AdWords much because they cannot target their customers neatly enough. They mainly use print advertising to reach their intended audience and do very little advertising on the internet . . . let alone putting money into teeny weeny text based ads and struggling with optimizing the ad so they are not charged an arm and a leg for clicks. Besides, if I was going to get them advertising on the internet I would try to get them to sponsor sections of my website before talking them into sponsoring the competition. Building advertising on my site has the added benefit of keeping my income independent of things like AdSense and giving me more control over how much I make -- whether on a per click or CPM basis.
I don't bother promoting both Adsense and Adwords. There are so many people that know about it already that it is quite hard to get traffic to these ads than trying to also convert them.
These referral ads are quite pointless. Most people know about adsense already. Would rather use that banner space for lots of text links.