#and most releases of it are the theatrical version because wide-screen is the default now

[mokeonn]

After doing a little bit of research (comparing the two different dvd boxes and playing with settings), it seems like the reason the better (extended) version of Muppet Christmas Carol isn't widely available compared to the lesser (theatrical cut) version is because it seems that the song cut is only available in full screen. There doesn't seem to be a wide-screen version of the extended cut available. So that's likely why the easiest to watch version is the theatrical cut, because Wide screen has become the default format.

And that's also likely why I didn't know there WAS a theatrical cut until after we lost and replaced the disk. The DVD we had was so old it only had full screen as an option, and the full screen version is the extended version of the movie.

Anyways, this is all just an educated guess. I didn't google the actual reason I just presume this based on what the boxes say, personal experience, and the fact that on the DVD that allows you to choose, full screen is the extended cut and wide screen is the theatrical cut.