It's not like the picture difference is small.
It's not like the difference is life changing, either.
I've never once watched a movie/sporting event/TV program in HD and thought to myself, "Son of a bitch, how did I ever watch TV without this?" It might be a better picture, but it's seriously not that critical; I've seen the difference between SD and HD, and I've never seen anything on TV, ever, where I thought to myself "Shit, I couldn't possibly enjoy this in SD. It's HD or NOTHING!" It's just not, by any measure, essential to whether I can or cannot enjoy what I'm watching on television and, frankly, I can't even conceive of why it should be.
I disagree. The difference on a properly calibrated TV is really really noticeable.