One person in the torrenting connection has to have port forwarding in order for the connection to occur. When you aren’t forwarding a port, you’re downloading from / uploading to only people who are. If someone has something you want but neither of you are port forwarding, you won’t be able to connect to them.
Once I got into decent private trackers, I stopped paying for Usenet. That said, it was great for when I was starting out.