It isn't though. For children under 13, COPPA [0] imposes additional requirements,so most sites have similar terms in their policies. From Instagram's terms of use [1], "You must be at least 13 years old".

[0] https://www.socalinternetlawyer.com/legal-requirements-socia...

[1]https://help.instagram.com/478745558852511/

> >Seeing that Instagram only requires the age of 13,

> That sounds wrong though

In what way?