It's been a political battle more than anything else. The hardcore people know a lot more about this than I do. But the basic idea is this:
The FCC decreed that all TV's need to go digital within a certain number of years because digital is more bandwidth-efficient than analog. Additionally, digital is so efficient that it can transmit 1080 interlaced lines of resolution to your set. But in that same band, it can instead send four lower-resolution programs. Many companies would rather send four times the content with four times the advertising. Satellite and cable would rather charge for four times the programming content. PBS has helped lead the way for 1080i.
If nobody sees the 1080i pictures in time, then the standards get set at lower resolution and it's over. BTW, lower resolution could mean the resolution you now see on a DVD, which most people feel is not too shabby (until they see 1080i, which even most electronics outlets are not set up to display).
So the race was on, and it looked like NYC would get HDTV. Two major networks were building multimillion dollar transmitters on top of the WTC towers and were due to start transmitting around the end of 2001. The terrorist attack wiped that out, of course, but the transmitters are now finished (I think) atop the Empire State Building.
Bottom line seems to be that the more people who actually see hi-res, the higher the chances of hi-res material being broadcast.
Good sources of info for this are:
1. The FAQ: http://www.samsungusa.com/cgi-bin/nabc/tech_info/tv/b2c_tv_dtv_main.jsp?eUser=
2. Dale Cripps has made bringing HDTV to the public his life's work: http://www.ilovehdtv.com
3. Where it's available: http://www.titantv.com
I am not associated with any of these guys. It's just that the technology is here now and relatively inexpensive to the consumer, and now is the time to get educated on it if we want it.