Employee when just starting, consultant when mature
What I've seen in Silicon Valley is that those who are younger tend to be employees of the various companies. When the person gets to have outside obligations such as family, they become consultants. So it isn't that those over 28 aren't working in IT. They're there. The younger generation, comes in and makes the same mistakes that were made ten years ago. Then the consultants who have more than ten years experience step in and clean up, but charge consultant rates to do so.
Outside Silicon Valley, you're "too young to get a good rating" until you're at least 30.