The core problem is that many people who apply for software developer jobs are attracted to the money, and just aren't very good at coding. Slogging through these interviews is a drag and a waste of time for capable developers. So, the process is delegated to junior people who don't yet have the judgment or experience to know what's important.

This is a joke, but uncomfortably close to the way junior people interview:

https://www.reddit.com/r/ProgrammerHumor/comments/4k994j/if_...