But the only people who write code as bad as QA folks do are the DevOps people.

The paradox of SDETs is: QA makes less than dev, no matter what flavor. If you're good at poking holes in developer logic, and you can code yourself, there's a 40-60% raise for you if you can switch into security consulting, which takes the same foundational skills and some reading.

So there are at least two brain drains for "good coder in test", and we aren't even the most lucrative one.