We are among the only industries that have multi-stage interview processes as the norm, including a gamut of usually quite gimmicky "technical" stages. It can now easily take more than a month to get hired as a software engineer, which is rather long compared to most other industries.

I think this boils down to the fact our field is young, there isn't professional accreditation in place or anything else for people to have a real idea of what you know without attempting to try assess that themselves (and failing miserably as assessing other people generally isn't their core competency).