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My first guess is there is a legal regulation when selling or publishing content that should be not available for non-adults. Any thoughts about this one related to US, Canada, EU and/or international law?
One of my old clients had that, in that every time you went on their public website, it'd display the "disclaimer" page until you ticked a box to move on. Also, one of their internal applications required users to tick a box saying they'd read some "news" before they could move on.
I tried to talk them out of it, but they were convinced it offered them some legal protection. Of course, it is unlikely, as everyone always ticks the box without reading the text, which defeats the whole object of the exercise.
This was also the company where the CEO insisted that he didn't want to log into the main business application, as he couldn't remember passwords. So, he "helped" by suggesting that his account, which was a super-user, should have no password. Eventual compromise was he used a space as his "password", although everyone knew it.
Bottom line is that it is a mis-guided attempt at "security" suggested by a non-technical lawyer, but makes the system less secure.
In the U.S., having a (registered) user click once to accept the terms and, again, when the terms are changed, suffices - there is no need for express acceptance at every login.
Indeed, depending on the circumstances, the user might be bound by the terms even without clicking. Please see Online Terms can be Binding, even if You don’t have to Click! Disclaimer: This information does not constitute legal advice and does not establish an attorney-client relationship.
I suppose if a company was doing something shady with its users, then it might want to be more proactive about showing the terms every time. The company could defend its poor practices by saying it showed the user at every login what it was doing and the user agreed to it. This isn't to suggest that the company referenced in the question is doing something like that.
Of course, a company has to comply with applicable law but that is a different issue.