Why pay for the game when you can go to an onion site that will sell you hundreds of compromised accounts that own the game for a fraction of the price?
At that time CS:GO would cost around $3 during various Steam sales and it was possible to buy a huge amount of gift copies that could be stored in your Steam inventory. So one "legit" account would buy lots of copies and then "gift" them to new accounts that would go on a cheating spree.