LOL, Many names that have a snap on them never get a NW bid or get $8.75 ones.
My bet, SnapNames and GoDaddy are well known to the retail market. NameWinner is getting there, but not completely.
There is one guy who wants that domain, he wants it bad. He goes to all resources he knows of, Snap and GoDaddy.
He doesnt know about NW so cant bid.
Just my guess.
I think NW is a little less popular becuase for people starting in Domains or not in the industry, having to give out your CC before you can become a member is a large step.
Especially when they dont know the performance. And NW's site design doesnt give a "proffessional" image, imo
JMHO.