Extending with Shared Libraries page - Missing explanation on why to avoid global variables

[moises-perez-tfs]

Problem with the Extending with Shared Libraries page, source file

Why would you recommend to avoid global variables just after introducing them? There is not even a reason why.

Avoid defining global variables with methods that interact or preserve state. Use a static class or instantiate a local variable of a class instead.

Possible Solution

I think an explanation would improve the undestanding of that notice/recommendation.