Why do people continually call Skyward Sword the worst selling 3D Zelda game?

[HoloDust]

Nogamez said:

HoloDust said:
I think those VGC numbers are correct, IIRC, not so long ago there was some Nintendo report where SS sales were included.

So yeah, while it might not be the worst selling 3D Zelda (MM is), it really didn't sell that well...which is a shame, it is pretty good game.

4 million not that bad though,  Any links (no pun lol) to that report?

Ah, it seems it's 3.67 after all, as of December 2014 - can't seem to find report itself (though I vividly remember seeing it in some thread around here), just this GAF thread that compiled all reports:

http://www.neogaf.com/forum/showthread.php?t=963700