[sebazzz]

It is more about backwards compatibility than anything else. Remember that .NET Framework is something that ships with an operating system (Windows) and has components built on this shared runtime: not only devtools like SSMS and Visual Studio but core Windows components like MMC applets and things like ADFS / Remote Desktop Gateway as well. This puts up a bar regarding backwards compatibility. Not only code that is written against the runtime need to be compatible, but also code hosting the runtime, debugging the runtime, the profiler API, and I could go on.

This yields some constraints in whatever is possible changing. Want to add new IL instructions? No can do. Need to change the debugger API? No can do.

Please also see this: https://news.ycombinator.com/item?id=18364032