They tape in HD so that if the show becomes popular and ends up in reruns in the future, they can be high quality HD reruns that people will watch as opposed to 4:3 NTSC reruns that will look like crap. They don't broadcast in HD now because that would require more satellite bandwidth and hence more $.
I read something about it being easier and more cost effective to "edit" material shot with an HD cam. I think they are trying to upgrade on the production side of things, and hoping that those of us watching are content with 480p. Granted, 480p is worlds better than 480i, so at least they are doing that, but I'm hoping they'll eventually start broadcasting in 720p. At least this method gives them that option.
Futureproofing programs seems to be the current trend. I just shot the aerial sequences for the movie "Trapped" which will air on USA Network sometime soon. We shot on Super35 with the groundglass marked for 1.78:1 HD with a 4:3 holdout in the middle. The finished film will get an HD transfer and be placed on the shelf. USA will air the SD version which is the 4:3 holdout extracted from the HD master.
It would have been cheaper to just do a Standard Definition telecine, but we composed the shots for both 1:78 and 4:3 so there will be both.
"Can I please just watch this the way it is supposed to be seen?"
"Can I please just watch this the way it was meant to be seen?"
If they are allowed to broadcast only 480p without being subjected to the wrath of the FCC or Congress, this leaves a huge digital data payload available for other profit-potential purposes. Broadcasting of the same 720p presentation significantly reduces this potential.