Loot boxes are the natural digital evolution of panini stickers and Pokémon cards from back in the day. It's been going on for decades, 5 'random' cards for a quid or whatever is nothing new. Just a captive audience in a new format, which parents absolutely must regulate in the same way they would in a shop with kids pestering them for a pack of cards at the till.
Regards the original question, you may feel good about gambling with the betting companies money, but it feels a bit mean spirited in the context of your housemate. It's like you're having fun on someone elses dime to make a weird point against someone who spends their own money on it..
I know kids have been exploited for years, with dubious tactics, but video games seem to take it one step further. Panini cards (I was into the Topps Garbage Pail Kids) were in a little box by the till usually, no lights or anything. If you had 20p you bought some if you wanted to. With video games, they're using the same colour schemes and patterns used in gambling machines that are used on adults. Once the kids start getting the buzz, the brain does it's own logic and it starts associating those patterns and colours with the high, and what needs to happen to get it. The vast majority will wake up eventually and realise it's a fools errand, but there's those who'll develop an addiction. They won't even see it as wrong because they've become so used to it, that it's normal behaviour for them.
My housemate and I have pretty much become a platonic couple (both our families have also started to socialise which is weird). She moved in over a decade ago, and we gelled instantly. She no longer pays rent (I'm mortgage free) and we've started splitting bills, co-own dogs, use one another's car, and she has more than her fair of say in what happens in the house. Because I'm also her main carer (she has a chronic condition which restricts her mobility at times) I do need to keep a bit of a heads up, mainly because she'll let it build up, and then when it's out of control I'll find out, and that's something else I'd need to take into account and pretty serious. She was also here when I developed the opioid addiction, and it was partly the amount of crap she (rightly) gave me that helped me to get clean. Even though I'm averse to pills now, she'll still remind me of it occasionally and what a total dick I was on them, and I'm simply throwing it back at her. It's never led to bad feeling, and I don't think we could resist saying something if our lives depended on it.