Microtransaction games are based around exploiting an inherent flaw in human reasoning; predatory behaviors that exploit our weaknesses as humans should be regulated against.
edit: to back this up: The wordpress blog linked below references 19 clinical studies and explains in detail much better than I care to write up.
https://platinumparagon.wordpress.com/2017/11/16/the-psychol...
When people start killing each other, or letting their lives fall apart around them, just so they can spend more money on another cute girl in Fate GO, then I'll let you make that analogy.
Gambling, video game, and internet addictions are real and do ruin lives.
While I don't want to dive into hyperbole territory and don't blame video games for this instance of violence, just this week someone punched and killed their 1 year old child because they lost at a video game[1].
Brains are weird and are easily highjacked by dopamine hits, whether they're obtained from drugs or external stimuli.
[1] https://people.com/crime/dad-allegedly-kills-baby-son-punch-...
But that does not make it harmful or predatory. People are allowed to spend money on whatever they want, just because you don't agree with their choices doesn't mean you should make it illegal.
In China these days, parents pretty much do treat smartphone games "as bad as drugs" for kids.
Rooting phones to prevent game installation and removing/breaking/locking payment APIs is one of most popular services in phone repair shops.