Don't get me wrong I believe there are certain things kids should only be exposed to once they are at the appropriate age. I myself was probably one of the last kids too get a modest mobile phone in my class for example. Especially in this day and age it is important to not train your kid as a screen-junkie from young age onwards as tempting as it may be for young parents. As you rightly mention, this also means parents have to keep their own habits in check.

Please understand that my point was something else. Even with surveillance and bans you can't shield a kid 100%. At school or outside it other kids will bring things your kid will get in contact with. Obviously turning your kid into an forcefully isolated hermit to avoid that risk isn't a good solution, because it comes at a cost. The better solution is to prepare your kid to be confident and rational enough to draw the line themselves as you may not always be there when it needs to be drawn. And you do that be repeatedly let them judge small risks themselves while you're present while showing them you trust their decision.

In practise that basically means letting your kid do things where they could eventually fall and hurt themselves instead of helicopter parenting and padding them in safety cushions constantly.