Why is it "illegal" to backup my games?

[Hephaestos]

Galaki said:

If my disc got scratched, the publishers aren't going to send me a new disc.

So, why is it illegal for me to make a copy of my own disc so I can safely store the original?

Why can't I mod my Wii so I can store all my games that I legally purchased onto a HDD?

ihad my diablo 2 disc crack in the player and looked it up (2000), bliz did offer to send new discs... at a fee 10$.

 

i have a 360 game that's unusable due to a scratch it got from the console...