management can't tell who is valuable. I am senior IC but even with cloning people's repos it isn't particularly easy to tell how good someone is.you have people who speak very confidently but don't make good code, in those subtle details that make the difference between 90% chance of serious bugs per project and 25%. Nor the difference between able to fulfill a one sentence requirement with specific technical language vs needing ,"add this to that function and this to that function then make a configuration item to control it." And maybe all the shy smart coders aren't usable with some management styles and some great managers can coax excellent work out of all sort of people.