It's probably true that in software, there are fewer companies that make silly revenue per employee. I work in "traditional" industry, meaning the revenue we make is for saying widgets we make in factories. Having 10% profit margins or 5% yearly growth is fantastic in our industry. In the US my feeling is that a larger fraction of developers work in the type of tech that has higher room for growth. And more importantly, the entire industry has to compete pay wise with these tech companies that can pay based on exponential growth and almost unlimmited properties (like FAANG). Since I don't have people across the street making twice my pay because they work at a FAANG, there is less of that.

The markets might be more competitive, which means less profits.