For most things the talk pages will explain why it is restricted, but if someone forgot to put a notice there, there's also a giant list of "the following topic areas reliably attract disruptive editing and get people angry, so admins move much more quickly to restrict editing than they would otherwise." https://en.wikipedia.org/wiki/Wikipedia:General_sanctions#Ac...
For most things the talk pages will explain why it is restricted, but if someone forgot to put a notice there, there's also a giant list of "the following topic areas reliably attract disruptive editing and get people angry, so admins move much more quickly to restrict editing than they would otherwise." https://en.wikipedia.org/wiki/Wikipedia:General_sanctions#Ac...