When you are writing for a platform that controls 98% of the market its less a choice and more a mandate. As anyone that has had to write parallel code in HTML

When you are writing for a platform that controls 98% of the market its less a choice and more a mandate. As anyone that has had to write parallel code in HTML/CSS/JS for IE vs every other browser your choices are: do it our way. MS was only open in their willingness to assimilate other good technologies, and then lock everyone else out once they had enough influence.