When the new Star Wars video game, Battlefront II, was made public in a final testing session before a general release, it didn’t receive quite the reception its publisher, Electronic Arts, was hoping for.

It featured a confusing mixture of virtual collectibles and randomised rewards that could be used to unlock characters within the game, meaning it would take 40 hours of continuous play to access just one top-tier character such as Luke Skywalker. The system, though, could be shortcut with cash: players were able to spend real money buying so-called “loot crates” full of the required rewards and credits. Just a few thousand dollars was all it would take to unlock every character in the game. A bargain! What’s more, these loot crates were also randomised, with users not knowing what they were getting before buying.

The fan backlash to this system, on social news site Reddit and elsewhere, was immediate and furious. EA eventually “paused” the real-money purchases, and slashed the time to unlock the heroes by a quarter. “Sorry we didn’t get this right,” EA said in a statement.

But loot crates are widespread across the games industry. The hugely popular football game Fifa, for example, offers access to new footballers through a loot crate system. Shooter game Overwatch hides desirable character “skins” behind loot crates that are also time-limited – buy them in one particular week or lose them for ever. The new Call of Duty, the blockbuster shooter game, also makes use of them.

Increasingly, players and regulators are questioning whether the concept has become exploitative and habit-forming.

Dave, a primary school teacher from Limerick, Ireland, says these mechanisms have resulted in numerous issues at his school. “We have had a few one-off purchases [within games] of over €500 (£447) on a number of occasions now, as well as many in the €100-€200 range,” he says. But more concerning for him are the children regularly spending smaller amounts, like €20 a week.

“Kids have all the typical responses that adults have to gambling in these transactions, (anger, disappointment, the urge to spend again to have another roll of the dice), without any of the impulse control and awareness that most adults have,” Dave says.

The problem is not just that loot crates offer virtual rewards for real money: it is that the way they do so bears more relation to a slot machine than a simple shop. The contents are randomised, with a hierarchy of rewards – some rare, some common – and no way to be certain if you will get the item that you want. Every aspect of them is micromanaged, from the probability of a rare reward to the visual animation of “opening” the crate, in order to maximise the excitment – and encourage users to buy more.

Currently, the legal background does not view loot crates as gambling, since the items received from them do not have a real-world value. But that is starting to change: regulators in Belgium, the US and Australia have all expressed concern about the practice. “Mixing gambling and gaming, especially at a young age, is dangerous for the mental health of the child,” said Belgium’s minister of justice, Koen Geens, after his country’s Gambling Commission launched an investigation.

The backlash only looks to be growing: EA has pulled loot crates from another game, Need for Speed, while Labour MP Daniel Zeichner has raised the issue in the UK parliament.

“Software developers and platform holders may argue about their legal definition as gambling but the ‘boots on the ground’ view shows that there is very little difference to children and the behaviours it promotes in them.

Responding to criticisms of its Star Wars offering, EA said the loot crates “are not gambling” and that “a player’s ability to succeed in the game is not dependent on purchasing crates.”