I ignored a job advertised in the paper once because it said it required a master's in CS. I had a bachelor's in mathematics. The job was for a Unix kernel and system hacker at a company making Unix workstations. This was around 1984, when Unix internals experience was not widespread.
Several months later, a headhunter sent me to interview for that job, which was still open because they hadn't been able to find anyone with the necessary Unix experience before I applied.
I got the job.
They could have had me several months earlier, and without having to pay several thousand dollars to a headhunter, if they had not stuck on that requirement for a master's degree in their ad in the paper.