Say you were a guardian or parent and get to decide when a child can get a phone or use a computer and get internet with it. If you wish you can also install software and change router settings to what you see fit.
Some parents decide to forbid the internet completely, others are more relaxed. Some go the helicopter route, and some do not care whatsoever what their kid does online.
What is your policy on letting a child use the internet?
children under 12 should not have one, it has been shown they actually have problems reading and writing in HS, and doing math. 13+ they can have it, assuming they arnt trying to do something illegal, like stealing credit cards and buying games or whatever.