Remember that a lot of men in the 18-30 range have been using lootbox mechanics in games since their teens. Or at least similar game mechanics where you are rewarded for taking a risk or loyalty with a random reward (loot tables, daily login rewards etc.).

I think a lot of gambling related material is targeted at the ages below legal gambling age with the specific purpose to get people to start gambling from legal age, however that would be hidden of course. Similarly no one becomes an alcoholic or smoking addict overnight the day they become of legal age for that substance, there is a buildup period.

Gambling addiction is way more damaging the younger you get in touch with it.