They'd also not want to spend the money that way as doing 20+ episode orders leaves less room for 10+ EP credits to grift off the top while watering down the scripts to appease each exec. That budget has to stretch, the scripts must keep people's attention each week even during bottle episodes, etc.
Lost only existed and became the show it was because network television was able to financially support the production of six seasons of about 18-25 episodes each with high production value
