Why should it be illegal? Framed from the other side, people are willing to take less salary if they live somewhere more affordable. My mortgage is half the price of my last apartment in the Bay Area, and while I won't take half the salary of my Bay Area job I'm not going to cry over the 15% difference between what companies are paying for locals out there and working remote out here (which is competitive with local companies). In some ways it makes me more marketable as a candidate.
There are many things about employment that should be illegal (at-will employment, enforceable non competes, ownership over IP, etc) but taking away the ability of either company or candidate to determine their compensation is a terrible idea that makes outcomes worse. It's as bad as banded salaries or any other kind of standardized pay scales.
Look at Chisel. I agree that C/C++ is the wrong abstraction but that's because using a HDL is more like meta programming in a declarative markup language that needs to be embedded in a higher level language for automation and verification than to compile imperative operations into silicon.
Lookup tables are the big thing that break CPU and GPU programs since at relatively small sizes you'll hit the memory wall. A lot of algorithms like media codecs (audio, video) and pretrained neural nets are trivial to design with HLS and have a major performance advantage over using a CPU or GPU.
Add in the fact that CPUs and GPUs are expensive as fuck, in short supply, demand high power, while FPGAs are pretty cheap and efficient since they don't do much you're going to find a lot of designs that call for them over a beefy and expensive chip.
That said, arm and risc V cores are dirt cheap. If your algorithm isn't hitting the memory wall it probably isn't going to be faster via HLS.