Wii Play on top of the software charts?

Amazons top software chart not only shows 5 Wii and one DS title but the top title is Wii Play!?!

01. Wii Play w/ Remote—Nintendo (Wii)
02. Rock Band Special Edition—MTV (Wii)
03. Mario Kart w/ Wii Wheel—Nintendo (Wii)
04. Wii Fit—Nintendo (Wii)
05. Super Smash Bros. Brawl—Nintendo (Wii)
06. Metal Gear Solid 4: Guns of the Patriots—Konami (PS3)
07. Assassin’s Creed—Ubisoft (360)
08. Guitar Hero: On Tour—Activision (DS)
09. Assassin’s Creed—Ubisoft (PS3)
10. Diablo Battle Chest—Blizzard (PC)

Wow, that many people are really still buying Wii Play? I know causal games have lower drop off rates but really... WFkitty...

[Source]