You're just wrong. The CSS box model as specified by the standards was totally unusable for making a website where you want boxes to have certain sizes with certain margins and paddings, especially in the days before you could use calc(), so you couldn't mix pixels with percentages. It's true that it was the standard, and so MS should have implemented the standard, but it's also true that what MS shipped made way more sense and every frontend dev turns on their box model when it box-model: border-box became part of the standard.