The point is that the entire system of 'crate that needs to be unlocked with a key for a random reward' is in itself already a form of gambling, especially as the various rewards have a value through the steam marketplace.
The paid loot boxes and skins with actual cash value that are integrated into CSGO and TF2. You can gamble inside the game without any third party tools and get your cashout as steam wallet funds or use a third party website to cash out for money.