"StackOverflow’s survey on age shows that there are just about 13% of developers after 40. Where are the others?" Not wasting time filling out online surveys? I'm not even 40 yet and I realised online surveys were a waste of time years ago. :-) A stackoverflow survey doesn't measure the answers of stackoverflow users. It measures the answers from the specific demographic of stackoverflow users who are inclined to ans…
There is still some truth to it. I'm 37 and have had to repeatedly and forcefully turn down managerial roles. The idea of horizontal growth is a hard sell to people who've chosen the vertical path. It would be very easy to drift into a management role, and in fact it happened to me once and I had to take deliberate action to get off the management track. I don't want to manage people. I want to build, and learn about…
I do consulting and freelance development now, and my success is in a large part due to the people skills I developed when managing others. You learn a lot about the many different ways people work (and don't work), and you learn a lot about yourself that you'd never see otherwise.
You learn how to mediate differences. You learn how to spot interpersonal problems on the horizon and head them off. You learn how to protect yourself. You learn how to promote harmony and goodwill. You learn how and when to compromise. You learn how to cooperate better. You learn to hear peoples voices. You learn how to be worthy of respect.
Without these skills, you'll forever be at the mercy of the prevailing political and emotional winds. The satisfaction of knowing you're 100% in the right won't unsink the ship.