It's true that x might not be able to converted to fiat or resold.
That makes it effectively equivalent to a raffle, which often put restrictions on reselling similar to these cases.
Raffles are considered a form of gambling, and are heavily regulated, in the UK[0] and Australia [1].
[0] http://www.gamblingcommission.gov.uk/for-the-public/Fundrais...
[1] https://www.vcglr.vic.gov.au/gambling/raffle/licensee-resour...
Even schools - noting you can't promote gambling to children - get away with that regularly. With those loopholes, you could probably get away with a lot.
Schools can run them fine, as most schools fall under "charitable organisation", so they just need written consent from the board, and a prize less than the state's maximum unlicensed game competition amount. ($5000 in Victoria, $2000 in Queensland).
[0 PDF] https://publications.qld.gov.au/dataset/fc2f9cdd-8799-45bf-9...
Sure, you can't convert its items into money, but you can convert them into wins in the game. And it has a "random" item drop system that's known to be rigged.
No exchange takes place. No fiat is given for a chance to open a box.
If I buy a video game and play it and occasionally get loot boxes that may have ultra-powerful items or may not, that's gambling. But if I buy a video game and play it and occasionally get items that aren't called loot boxes but may be ultra-powerful or may not, that's not gambling?
Why do you hide the repeated purchase?
The game is bought, once.
Loot-boxes require another purchase - an uninformed one. You purchase an item for a chance at something else, a chance that you don't actually know.
Mario Kart would be gambling, if you had to buy every crate as you hit it. As it is, with no additional purchase, it is simply a randomised strategic feature. Currency of some form needs to be exchanged to create gambling.