I have never once filtered someone for lacking confidence. I have never seen someone filtered for lack of confidence by any panel I've been on or any panel I was the hiring manager for. At this point in my career I have interviewed ~1000+ engineers.
I think you're interviewing with the wrong people, or at the wrong places. Way too many people treat interviewing as a way of demonstrating intelligence via computer science trivial pursuit. 5 minutes with Google will demolish 99% of the questions you might ask if all you care about is getting correct code on the board. The interesting part is the process and discussion the code creates, not whether or not they know the secret handshake.
That's nice, but I have literally read interview feedback from very smart interviewers at multiple companies that vetoed candidates because "they didn't appear confident". This isn't something I'm making up: it's a real problem.
I think we can both agree that interviewing is overdue for a radical reboot. Silicon Valley, disrupt interviews, please!
That said, there are places that don't interview the way you describe. I'm equally sure there are places that do (I vividly remember my Dropbox interview). My hope has always been that Darwin's Law will apply to such places over the long run, but instead I think what actually happens is that as these organizations grow the interview process just ends up being a diluted version of the same BS, which translates into "lowering the bar." Nevermind that your bar was curvier than Lombard Street.
I think you're interviewing with the wrong people, or at the wrong places. Way too many people treat interviewing as a way of demonstrating intelligence via computer science trivial pursuit. 5 minutes with Google will demolish 99% of the questions you might ask if all you care about is getting correct code on the board. The interesting part is the process and discussion the code creates, not whether or not they know the secret handshake.