That's only a fraction of the problem though. You have no idea how easy it is for for example, kids on the fortnite subreddit to end up on the NSFW fortnite subreddits and talk to others and start exchanging pictures.
The other thing nobody wants to talk about is that it's not always adult creepy men approaching kids, it's the kids themselves that seek out sexual conversations with strangers on the internet.
Sure, this is also the parents responsibility. But even with open phone access, internet filters, etc they will find a way, especially if their school gives them laptops and there's open wifi everywhere.
That's where this is also for. Parents cannot monitor all their children's internet access at all times. Children will resist and find ways around parents' control, as it has always been.