What is the deal with Tracking Threads?

This might be a duplicate thread but if it is you can close it.

All I want to know is why are some tracking threads like the Q400 ones fine and the 777 threads are not? I have been curios and I have always wanted to know. Like me I know that other people are wondering the same thing. So if people can tell me, What is the deal with tracking threads?

Thank You very much.


I think some are closed and others left open is because they can easily go off track, by having people requesting liveries there.