Actually, that's not entirely true either...
1920 x 1080 resolution screens are displacing 1920 x 1200 resolution screens in both laptops and monitors because they are cheaper. LCD panels are cut from very large panes of "LCD glass"; I think some panes are as large as 12' x 7'. You can cut more 16:9 panels than you can 16:10 panels from each pane. Therefore, each individual panel can be sold at a lower price to recover the cost and to make a profit.