I wonder if part of it is that some techies who aspire to management do so because they don't actually like developing software.
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.
I'm in this boat at the moment (one man band contractor of many years finally starting to take on employees). I'm finding that as I delegate more of the routine day-to-day work away, I'm actually finding myself with more time to play around with new stuff. Trouble is, in my line of work (corporate .NET stuff) customers aren't interested in anything new and exciting - they just want Windows applications and ASP.NET forms connected to SQL Server databases.
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.
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.