I think a big part of the reason is that embedded software payscales seem to be closer to EE pay than typical SWE pay. I've never understood why but from what I can tell the more specialized EE knowledge is not valued very well. I had a colleague who moved out of embedded software to become a backend developer for this reason.
There's thankfully some room in the market for pay reasonably comparable to typical SWE payscales, but most embedded developers live in their own little worlds largely disconnected from trends in the rest of the software industry. They're often simply not aware of what they're worth to demand it and the kind of companies that need embedded developers tend to be both unable and unwilling to pay those rates.
That’s pretty much my situation, I originally did electronic engineering and firmware but have switched professionally to backend software. Partly because of the pay, but mostly because the tooling and quality of most embedded software is so painful to work with. I’d rather have an overgrown dependency tree than a debugger which crashes more often than not.
