There was never a deliberate effort from TC to ignore StackOverflow, I linked to it in some of my posts there.
IIRC we simply were not in the loop on their news, announcements or tips.
A lot of the TC'ers use Quora which is why it is mentioned a lot, but in TC dev we were definitely big fans of StackOverflow, its just that the full-time writers didn't use it or notice it as much.
If you look at Techmeme, you can see that StackOverflow hasn't been getting much attention from the usual tech blogs:
I figure it is for the same reason - they weren't actively reaching out to the tech bloggers and instead using their own blogs for PR. Still worked out well for them :)
I'm not saying that with any scientific basis, but rather on the basis that a much larger percentage of the startup community seems to be active there than on other sites.
Often when you see someone ask about a random startup you'll get the startup's founder or an investor answering, something which you rarely see elsewhere.
For such a long time TC have deliberately refrained from mentioning/promoting StackOverflow.
Thank you guys (the SO team and the contributors), for providing such a valuable website for programmers.