Their strategy relies on fragmenting the browser space. So, they have various subsets of various versions of HTML, each supported by a different browser on different platforms. All that so you can't deliver web applications easily.

Companies who swallowed their poison pill in the early 2000's and built their intranets dependent on IE 6 are feeling the pain now, having to deploy intrusive security measures that don't really secure anything while shouldering the cost of "upgrading" the apps to browsers that run on the OS they want to deploy.