Why do I get better results using the search websites than I do using this super search option?

I have been using USENET for a couple of years. I use Newsleecher as my news reader. I do have the super search feature but, I seem to have trouble finding things with it.

It does find things. But there are many many occasions where I only find the files are looking for using search websites like nzbsrus. I can find a file using the websites and the file won't even show up on super search even the file is well within super search retention.

Why do I get so much better results using the search websites than I do using this super search option in Newsleecher? Is there any other reader program with a searching program you guys can recommend?