I think those stickers were useful for me and my classmates to learn about economy when I was a child. We traded with them and the rarest ones naturally fetched

I think those stickers were useful for me and my classmates to learn about economy when I was a child. We traded with them and the rarest ones naturally fetched very high values (in terms of other stickers), so we got to experiment scarcity of resources, supply and demand, etc. I never thought of opening a random pack of stickers and gambling, but you definitely have a point. It is not trivial where to draw the line. In my case, I had a lot of fun (and no gambling addiction) with stickers, and even more with Magic the Gathering a few years later! (and I made some actual money with MtG card speculation when I was like 14). Virtual loot boxes I see as quite evil though, I need to think for a while on what the differences are. Perhaps it's just prejudices due to my age but I never knew stickers or MtG gambling addicts and with loot boxes there seems to be much more risk of addiction.