I wasn't sure, but figured this is the most likely reason, rather than upgrading this particular product. Unfortunately, I don't think you were alone on this (particularly for owners of the 1080P variants).
Well, I guess the only good thing for me at the time was that it wasn't very difficult to sell (high demand, limited numbers) for my asking price. I bought the set new for around $2k in a closeout sale and sold it two years later for $1,500. It sold within 3 days of posting it on Craigslist in LA. That's something that NEVER happens with most TV brands.