>Writing code is not hard.

Writing code has a minimum IQ requirement; a significant fraction of the population will essentially never be able to code by themselves. That labor supply limitation is what's kept programmer salaries relatively high.

Writing code doesn't have a notably higher (if at all higher, vs lower!) IQ requirement compared to some of the basic components of EE or MechE work. Programmer salaries have been driven up by the ability to write-once-sell-globally and the dramatic profit margin difference between that and, say, producing chips where there's a much higher fixed cost due to the need for more real material, tooling, etc. Many of those roles require a much higher-than-baseline-skill, but it pulls up the compensation competition for almost everyone else too. (Though even then there are a lot of unglamorous, line-of-business, internal-tools-programming work that's not paid particularly well even in a lot of parts of the US far from the big tech companies.)

I've watched dozens of people try to learn to code and fail, some definitely not for a lack of trying. Of those that did learn, only a fraction had the IQ or passion to be genuinely good at it.

The difficulty of it has absolutely been a bottleneck to the supply of good devs, keeping salaries high.