Steam's VAC (Valve Anti-Cheat) and game ban systems can block people from playing games they have cheated in, no questions asked. But where there's a will to break the rules, there's almost always a way. One tactic Steam cheaters use is to stockpile giftable versions of games on one account (often during Steam sales) and then pass them on to accounts that they only give between 0 and 0.00001 shits about. This way, even if they cheat and get banned, they live to cheat another day.
Valve has changed Steam's restrictions to combat that. In a recent update, Valve wrote:
In response to this problem, Steam no longer allows users to purchase copies of VAC or Game Ban enabled games to their inventory. Additionally, if an account has directly gifted a game to other players who have been VAC or permanently Game Banned, then that account will lose the ability to gift that game.
We've taken these steps to ensure the integrity of the multiplayer experience for those participating in online gaming communities. We understand that the restrictions on buying to inventory may be inconvenient for some legitimate users, but we believe that these steps will reduce the number of cheaters you'll play against. And that's important in having an online gaming experience that's fair and enjoyable for everyone.
Some people are upset that they could have a spotless record, unknowingly gift a game to somebody who chooses to cheat, and lose the privilege of gifting that game permanently. Other people are suggesting it might hurt individual people's ability to do things like giveaways.
That does kinda suck, but I guess the best solution is to only gift games to people you really trust. And if you're doing a giveaway, see if you can get codes, rather than giftable game copies. Broadly speaking, I think these changes make sense, but in specific cases like the ones above, the situation is far from ideal.
Personally, I don't use the gifting system all that often. Usually I buy a few games during holiday Steam sales and gift them to friends/relatives. That's about all. How about you?