Why is Wii Fit deemed 'casual' yet Guitar Hero isn't?

[DoesWhatNintenDont]

RolStoppable said:

WiiFit is from Nintendo and for a Nintendo system. Guitar Hero started on a Sony console, DDR in the arcades and later debuted on a Sony console.

Basically I think people who really dismiss WiiFit, hate Nintendo in general and the Wii specifically.

EDIT: I really like HappySqurriel's explanation.

Nitpicking here Rol, but Guitar Hero is a complete rip off of Guitar Freaks which was an arcade game right up there alongside DDR. 

My local arcade were I grew up had several installments over the years of it. So the idea was very established before Guitar Hero came along.