The problem is that most techies who move up to management don't have Carmack's brain. This guy is a machine! For a normal person, it is almost impossible to get a workload done that's comparable to Carmack's.
As an individual contributor I can't imagine giving up my day-to-day coding for a management position. Management responsibilities, sure. I'd wager that most software developers who are given enough autonomy are doing a lot of micro-project management anyway.
Giving up on researching new technology and playing around with stuff? Not a chance.
Of course, if you're lucky enough to be in a job (I'm thinking frontend web) where playing with exciting new tech is part of the job, I can absolutely see how the move to management and the loss of overall hands-on time with the code can be a bad thing. Thankfully for me it's been somewhat liberating.