Valve has disabled the PURCHASE AS GIFT function for CS GO.
You cannot buy CS GO as a gift anymore during Steam Summer Sale!
This is Valve's way of cracking down on smurfs and resellers.
Valve's official reply regarding not being allowed to buy CS GO as a gift:
CS:GO will not be giftable during the sale. Our goal with sales is to grow the community and historically, during sales, the new users that stick around are mainly the ones that purchase copies for themselves.What are your thoughts Counter-Strike: Global Offensive community?