bad 3/6 players and $20 SNGs

[Rhone]

My regular game is Party 3/6. For kicks the last few months I have been playing the occassional $20+2 NL SNG. Every once in a while someone at my SNG table will have notes I've taken on them at 3/6, and almost inevitably they are among the worst players -- typically LP-Ps with 68% VP$P or something like that.

Naturally, I've come to wonder why. Are $20 SNGs where bad limit players go to die? What's going on? Does a decent 3/6 player who wants to mix it up with SNGs typically play much higher buy-in games?

Just curious what others think...