The reason for this is that the skills of an IC at that level are simply not needed at most companies outside of ones that have pure tech as their differentiator. What would a consulting body shop do with a rockstar engineer who invented a programming language or scaled a database to a load previously considered unachievable or created a new industry-standard cryptographic algorithm? A manager who can work a team of 5 junior-mid level engineers to the bone to meet an arbitrary client deadline with "good enough" work is a lot more valuable.