Why does playing online change my video settings?

[deluxxe]

I've never been a huge fan of playing basketball games online due to the cheese factor, but i decided to give 2k13 a shot online
FIrst thing i noticed is that the framerate was lower and I was getting massive screen tearing. It looks like playing online forces v-sync off. I've never been able to play video games with v-sync off as the screen tearing gives me a headache.
Anyone know why online mode would force v-sync off? Or if there is some sort of fix I can do to force it on?

[JaoSming]

if you force vsync through your graphics card control panel it should stick

framerate is dependent on both players' machines and connection strength

[deluxxe]

thanks for the reply. Forced v-sync on and fired up fraps so i can bail out of low fps games now.

Still not sure why they would turn v-sync off though