You have to remember that these web designer's are the ones doing the work. you cant expect them to show 100% dedication to a project they don't work for and for free? i mean really i know its a free service but free services have limits! i think the artists should choose on what projects would fit their interests.
It's called Charity and "doing good deeds". Tell that to the millions of people who are part of the Red Cross, St John's Ambulance and numerous other charities who give up their time (for free) to help others with 100% dedication.
Let's imagine I'm selling GT "Choco Bars" on my stall. Today, I'm being particularly generous and offering them for free. I've even put up a sign saying "Free Choco Bars for anyone who wants one". Unsurprisingly, because my Choco Bars are so popular a large queue forms. Unfortunately, I don't have enough Choco Bars for everyone in the queue, but I can make some more, it will just take a while longer.
Now, what's being suggested here is that, I can freely walk up and down the line of people queueing for my Choco Bars and hand them out to whomever I want. Next, I can hand out some "Extra Tasty" Choco Bars or "Low Fat" Choco Bars to some people in the queue merely because they're "Upper Class".
Now ask yourselves, is this fair? I'm not suggesting you churn them out as fast as possible, I'm suggesting that you just operate a fair system.