Microsoft prides itself on extending backwards compatibility as far as it reasonably can. Hence the "legacy" mode that maintains the traditional Windows desktop

Microsoft prides itself on extending backwards compatibility as far as it reasonably can. Hence the "legacy" mode that maintains the traditional Windows desktop/UI and support for browser plugins. Everything in new shiny Metro land is a clean start, so it's reasonable to say "We aren't going to support ActiveX controls in the browser anymore" there.