Using Event Viewer, I can access the event logs on remote PCs

I shall call these PC#1, PC#2, PC#3 and PC#4

On PC#1 I can access application, security and system
On PC#2 I can only access application and system
On PC#3 I can only access application and system
On PC#4 I can not access any

PC#4 could be due to anything so I'm not too botherd about that.

What is stopping me from accessing the security logs on PC#2 and PC#3?
Thanks