Can we create giveaways that's not a key?

So the only possible choice for me to giveaway the game is to buy it from Steam store and then gift it by sending them to a friend on my friend list.
But when I try to create a giveaway here, the section with keys is required to be filled. I have no other choice to fill it with the text like STEAM-GIFT-WILL-BE-SENT-THROUGH-STEAM or something like that. And a lot of users understand that, but I met some that have Private profiles and refuse to add you, one person even blocked me.
Can you guys believe this, when you just tried to add someone and they just insta block you...