This. Not breaking user space is fundamental to the success of most operating systems today. I read this article I cannot seem to find about Microsoft employee

This. Not breaking user space is fundamental to the success of most operating systems today. I read this article I cannot seem to find about Microsoft employees spending months replicating "wrong" behavior in <oldwindows.. win95?> so that applications still ran on <newerwindows... win98? win2000?>. Users don't want to see their applications crashing. I wish I could find this article again, it's very relevant to your comment.