Most software ultimately automates menial labor. If the menial labor that's being automated is highly paid, the software engineer is highly paid. If the menial labor is lower paid, the software engineer is lower paid. Adjusting also for the amount of menial labor which is automated.

In a poorer society equivalent menial labor is more poorly paid than in a richer society. Edit to add: And in a poorer society some of the highly paid menial labor that exists in richer societies may just not exist, or at least not in the same amount.

Wages are generally controlled almost entirely by supply/demand. In an area where there are more people interested in doing a job than there is in demand for that job, wages for that occupation will trend towards the lowest possible value. In an area where there is more demand for a certain skillset than exists, wages will trend to the maximum affordable cost for anybody with that skill.

All the other stuff like expertise and value is, counterintuitively, near irrelevant. For instance postdocs are some of the most highly educated and ostensibly highly skilled individuals - and many have taken on hundreds of thousands of dollars in debt to get to where they are, yet they earn about as much as a plumber does, because there's far more supply of postdocs than there are jobs/positions for them.

So putting all the theory into practice. There are usually three possible reasons. Supply is too high = excessively high rates of software training/education. Demand is too low = not many roles for software developers. Or the companies that are hiring aren't making much themselves so the "maximum affordable cost" is relatively low.