The things you have mentioned are rather trivial in the overall picture and really not a good enough reason to support IE7 but not IE6. The JavaScript engines

The things you have mentioned are rather trivial in the overall picture and really not a good enough reason to support IE7 but not IE6. The JavaScript engines are nearly identical and the broad set of technologies are the same. For example, I consider not supporting SVG 10 years after standarization a major probleam. And only IE9 addressed that issue.