Not all HD programming will be 16:9 aspect ratio (aka 1.78:1), some will be letterboxed such as the more common OAR 2.39:1 (35 mm anamorphic / PanaVision) There are other used OARs as well.
Letterboxing and pillarboxing of an OAR on 16:9 HDTV displays is normal and acceptable; stretching, cropping, pictureboxing and pan&scan are crap.
When will the need to explain OAR and HD programming end?
It's been over ten years since HD launched in the US.
If the OP doesn't get it by now, then he/she never will.
People replacing their old tvs are now doing so with HDTVs because they are only a little bit more in price then a non-hd tv.
It will end when 100% of the households have HDTV's. So, enjoy it because the question will be around for a while.