It could be, sure. But Google and Facebook aren't the primary employers of programmers in the United States. Other "uncool" firms such as banks, manufacturers

It could be, sure. But Google and Facebook aren't the primary employers of programmers in the United States. Other "uncool" firms such as banks, manufacturers, retailers, and small businesses employ the majority of software developers. Unless you insist that age discrimination is rampant across those industries too, I disagree the evidence supports your claim. I admit that it's suboptimal to only have one source, but the Stack Overflow survey appears to be representative.