Since he never was fleshed out as anything but a sportscaster on the Muppet Show, it's hard to really find a place for him. The Newsman was a bit similar in that he had a specific purpose and wasn't used outside of that but there's still much more opportunity (especially as society has become more media-oriented) to use an all-purpose news reporter than a sportscaster. Combine that with Jerry Nelson's aging/health issues that has kept him from doing more active Muppeteering and that's why he hasn't been around.
But as mentioned, he's also one of those characters that may turn up when one's not expecting it. His appearance in the first issue of Muppet Robin Hood was a suggestion by regular Muppet writer Jim Lewis, so that bodes well that those who write for the actual foam Muppets remember him and look for opportunities to use him.
They found a great way to use him in GMC. A decade later when the Muppets were doing weekly guest sketches on Good Morning America he also made a cool surprise return.
The thing about minor characters is the frequency of their appearances tends to be in direct relationship to how much major projects the Muppets get. When they don't do much, there's not as much opportunity to even use the secondary characters much less the smaller fan favorites. Here's where a regular series would benefit the Louis Kazagger's of the Muppet world!
But in the meantime, they're out there and remembered. Heck, even Kermit remembered to name Louis in his chapter on The Muppet Show in his biography...even if he didn't quite remember how to spell his name...