At the very least, all purchases should include info about the randomization. It shouldn't be legal to sell randomized products while keeping the randomization secret.
Lottery tickets include odds on the back of the cards. I think that has a very small effects on discouraging play. And those odds are pretty straight forward (1 in 2,000,000 for a 500k payout). I imagine information about how randomization works would be even more indecipherable.
Which supposed harm in this case, there is more than one.
Currently online games are free to swap out algorithms in realtime in order to maximize revenue. You have no idea what your chance of winning even is.
I hate the Lego minifig series, and Panini sticker albums, and Pokemon cards.
They should all have to include how many packets you'd expect to buy to complete a collection.
I don't think parents (or children) are aware of that, or have any idea how to work it out. (I didn't, I just searched until I found this wikipedia article: https://en.wikipedia.org/wiki/Coupon_collector%27s_problem