I mean, I think part of it is because they grew up interacting with apps because parents were, mostly rightly, restricting their children from use of the greater unrestricted web. Every modern parent I know had children who knew which apps on mommy or daddy's phone they were allowed to touch - their games or youtube kids or whatever. These apps provided easy safeguards for parents to rein in their child's internet experience. Even if these methods weren't perfect in their attempt (Elsagate and all that), this was still good practice for allowing your child access to modernity in the times you couldn't fully devote your time to overseeing their activity with relative confidence they were probably not watching wildly inappropriate content.

In a perfect world parents and educators would also be devoting time to teaching their child to navigate the internet and allowing them monitored (with physical eyeballs, not tracking) online browsing time, but I don't think we can rightly fault the kids for not having received that. Rather than grumbling about the situation, I think we'd be better served accepting it for what it is and instead approaching the topic from a stance of: how do we teach them better behavior and help them unlearn these bad habits?

edit: typo