Or perhaps the people that can best fill these positions are foreign nationals and the wages have already been driven higher in competition with the number of them coming in for engineering positions? People have mentioned foreign language expertise as a big need for these where the pay is not commensurate to SV-style companies, and this includes positions in education, non-profits, etc.

Even in for-profit industries, margins are not always high enough and competition is often fierce enough that they cannot afford to raise prices to raise salaries.

There are a lot of important industries where margins are quite slim.