Why does C#/CLR not support method override co/contra-variance?

Question

There are quite a few questions & answers about hacking around the limitation of C# not allowing method return (and argument) types to be changed to compatible types on

Answer 1

Seams introducing covariance of return value has no essential drawback as Java and C++ have used. However, there's real confusion cased by introducing contra-variance of formal parameter. I think this answer https://stackoverflow.com/a/3010614/1443505 in C++ is also valid for C#.