Yes, it has surprised me to learn this. I have spent some time looking up some info on them on this forum. So far I have learned:
1. They are not important, but you should check to make sure the info is correct because they are important.
2. No one really uses them, but there is a lot of people who use them.
So far this is what I have found out from reading prior posts. As clear as a river in Tijuana!