Companies are supposed to maximize profits. They can easily outsource all engineering to cheaper places like India. Why do places like the Silicon Valley hire Americans when they can outsource the jobs? Is it just because of the time zone? Many companies even sponsor visas and call engineers from countries like India all the way to America and pay them high wages to work in the Silicon Valley offices. If the same engineer (with the same skills) stayed in India, the company would've had to spend 10x less money on them.

Why do companies choose not to outsource all engineering jobs to overseas, or why don't they open new office in these cheaper countries and hire engineers in their subsidiary offices instead of spending so much money calling engineers to the US?

Just curious why this is so. I'm not suggesting it should be one way or the other.