One of my biggest complaints with Steam is that it's basically an unlicensed casino with extra steps -- and one of the things you could do at one point was buy a "challenge pass" for a major tournament that was effectively a "pick 'em"-style bet on the outcome. There is no age gating on this, outside of a click-through prompt since the game is rated ESRB M/17+ and its equivalents.

1. You buy an event pass

2. The event pass contains a "coin" that can be upgraded, and grants access to a "pick 'em" interface

3. Based on the outcomes of the matches and your picks, the coin is upgraded

4. The upgraded coin allows access to "souvenir packages"

5. The "souvenir packages" and their contents (rare and/or unique weapon skins) can be traded on Steam's marketplace for store credit or currency