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!
There are also child gambling machines, like crane games, coin pushers, or that one with the moving light. I don’t get why stuff like that is okay. I’m not defending loot boxes, but I do think it’s really weird to single them out. Why don’t they just work to pass a law which bans all of them?