That's exactly the point that the game industry is refusing to acknowledge publicly/officially.

Let's run through the checklist:
1. Low chance of reward.
2. Encourages people to spend lots of money in pursuit of a goal most likely not to happen.
3. Causes addictive obsessiveness in pursuit of the grand prize.
4. Can result in financial hardship if the addictive spending overrides the common sense to stop spending.
5. Benefits the corporation by increasing income for no or little payout granted, minimal benefit to the customers.

Anything that hits all those checkpoints is gambling, there's no negotiation or debate.

I expect the companies know all this anyway, they just want to keep the system running because it's profitable for them.
And they'll probably do so right up until the day they're ordered to cease&desist by international law, just to squeeze the last few dollars out of a vulnerable playerbase.

For additional context, Star Trek Online and Champions Online didn't have lockboxes until Perfect World bought Cryptic Studios, then they suddenly appeared immediately after that acquisition.
I was told it was because Perfect World ordered Cryptic to make it happen, because they wanted it to be done.