One side of this that bugs the crap out of me: I have a PhD in math and, after getting sick of teaching mediocre students with a palpable aversion to mathematics, I spent a couple of years applying for data science jobs and getting very few responses. The few interviews I got seemed to go well, but I had no offers and gave up on leaving academics. I have experience in software development (C++), I have a portfolio of…
There might be a cost issue. Employers will see the PhD as raising salary expectations without adding value. The only real way to make inroads is to get a job related to your PhD and then do coding work. Typical interview for higher jobs aren't focused on tests or quizzes. If that's what your getting your not applying to the right places - and there might not be many places.
It could be true in some fields (biotech and life sciences, pharma/chemistry, "real" engineering, ...) but in math/CS?
Most companies hire PhD grads at one job grade/level above entry-level, i.e. it's typically not worth much more than a ~2 years head start salary-wise. If a candidate has spent 4/5 years gaining experience in the specific skill set you're hiring for, that's a bargain.