Official statement from Valve.
We shared with the NYAG that these types of boxes in our games are widely used, not just in video games but in the tangible world as well, where generations have grown up opening baseball card packs and blind boxes and bags, and then trading and selling the items they receive.
You’re right! We should stop that too!
I don’t care if they exist, but you’d have to make it an 18 an over type of deal. I don’t really care how adults choose to blow their money, gambling included. You want to verify you’re over 18 so you can get loot boxes, you do you.