Why would they? Pay is just much lower, despite the fact that there's way more responsability. I personally know more people who switch from hardware to software than viceversa.
I'd do anything short of murder to get out of software. If I could find a career that paid enough to live somewhere nice and didn't have the horrible working conditions that software does (stack rank, fake agile, unrealistic deadlines, stack rank, etc.) I'd do it in a heartbeat.
There is so much more to software than SaaS apps. I do compilers now for new chips. The work environment is so much better. Go for the hard problems always.