I'm Not sure in the US but in Australia its mainly due to a very strong LCD advertising push. When lined up next to each other i can not see why anyone would choose LCD but as Johnny highlights its not always a quality of picture choice. Its interesting to see some of the push back by a couple of companies here in australia Panasonic is running a very big "this is the advantages of Plasma Campaign" Pioneer with its new Panels are also pushing the advertising button more so the in the past. For me its the transition & the brighness LCD that just doesn't do it.
Why are LCDs more popular than plasma?
I have a rough time seeing differences in picture quality between brands and models, but the difference between plasma and LCD are overt even to me. When I go to bestbuy, fry's, etc. and gaze at their displays of flatpannels, plasma televisions just look beautiful, despite the reflections, while LCDs just remind me of working on my laptop. Is there more merit to the quality of LCD than I observe or is there some other reason LCDs outnumber plasmas?