Maybe that's because companies tend to hire whiteboard-master generalists rather than subject-matter specialists who may not be great at standardized technical interviews. ;-)
Also, if the company culture is ultra-bureaucratic, maybe the company should fix that instead of wasting months on every new hire.
Seriously, if a new engineer can't commit code within the first week, that's a company problem, not an engineer problem. Of course their code shouldn't go directly into production, but that's true of any new code. Give them something small to start, like some bugs to fix.
> That also doesn't account for complete cultural mismatches that cause instability in teams and hurt the impact of your other employees.
Technical interviews can't determine this.
> knowing its hard to get into a company signals to each applicant that the other employees there made it through that process.
I realize that's a signal, but it's not necessarily a good or accurate signal. I think it's mostly PR and hype. Reminds me a lot of fraternity hazing. Google engineers believe they're the best, and some of them may be, but some of them don't impress me at all. And as I mentioned, engineers tend to move from company to company anyway, so if Google engineers are "the best", they're constantly losing the best too.