$ env -i WLIST=$WLIST WLIST2=$WLIST2 command $ env -i WLIST=$WLIST WLIST2=$WLIST2 commandMy guess is that the unadorned `ONESHOTENVVAR=1 someprogram` is a little obscure to some. As to the lack of -i; it almost certainly necessary makes no difference to the result.
But for most part, it's probably just people copying-and-pasting stuff without really figuring it out what it does. For example, compare "exploit #1" and the supposedly different "exploit #3" on shellshocker.net.