I think it has something to do with how some people felt that Scooter was Richard, and that's still a wound they don't want to open. And apparently the thought was that Kermit was too important of a character to not keep around, while Scooter was expendable. Heck, I still can't listen to Scooter's lines in "Saying Goodbye" from MTM and think of what's happened to the character. Hopefully with his small appearances in MFS and the life Muppet Show at MuppetFest, we'll get to see him more often (hint hint, there are fans of Scooter who miss him, hint hint!).
I haven't heard of any stations in the US that are airing those three shows.
EDIT: Hold up! I think Skeeter may have been in a flashback in "A Muppet Family Christmas." I found a wallpaper that looks like it has scenes from that special, and one is a group shot of the Muppet Babies (as dolls/muppets) sitting on a staircase looking at a Christmas tree. And right above Kermit, half-shadowed, is a Muppet that appears to be Skeeter. But other than that, nothing.