One of the reasons there seems to be a market for the trade sites is for some reason the F&EL seems devoid of stuff. One factor seems to me to be you post what you want to buy or sell a month+ from now! Another reason I have heard is "I don't post because I don't have very many and do not want a bunch of buyers when I only have 3 pairs to sell"
Another thing the lists do provide is a market for obtaining new AKA members. Not many people will join the AKA that have never even seen a killie. "Gee I think I'll join the AKA, wait a month or two to get a package and then try to see if I can buy a fish!" Not a good incentive to today's "I want it now" generation.
I am an AKA member but not for the F&EL. If I had to depend on it to get fish, I would not come close to the varieties I have right now. I bought fish twice thru the F&EL. One pair in about 1968 and one trio a year ago. I have had great experiences with people AKA and non AKA and have not really run into "bad traders" but probably some people have.