Alternatively, as you get better and deal with complex issues and have more sophisticated thoughts, you realize that SO can't answer the majority of your problems.
That's what I've learned about SO: it's fine for popcorn questions, but for the in-depth knowledge and discussions... meh.
The older the developer, the less curious they are <= the less questions they have.
Of course you could say it's because the older developers are more experienced. But would that quality per se quell the thirst for new knowledge?
Just thinking aloud...