Question Regarding Steam And Cd Key

Why is it that people can sell Steam accounts with games properly done with CD Keys. But yet I can't sell a CD Key for a particular game. I have the CD's and everything if needed to post. (Diablo 2 + LOD). If you are thinking maybe the Keys are possibly banned (which there not, i've only used about 20 times, and still noob), how do you know if the steam VAC is good or bad, or how many servers the CD Key from steam is banned on...

Just a thought

 

a CD key can only be registered with one steam account. you could have already made your steam account and then sell the useless CD key.

 

Then whats the point of buying a steam account with lets say COD4 if the cdkey oonly works w/ 1 cpu?

 

because you can sign into your steam account for anyones computer

 

You still never explained why I can't sell a CD KEy for a non steam game. I have Diablo 2 andd Diablo 2 Expansion Lord of Destruction. Never be played again.

 

cd-keys are linked to battlenet accounts as far as im aware so if you have already created an account for battle net, they can't play online using that cd-key

 

That and it's illegal.
Well, breach ToS.

 

But saying that, selling steam accounts are a breach of the SSA

 

Because when you sell the cd key, you still retain that copy of the cd key, thus meaning two people playing on one cd key, thus meaning illegal.