It's interesting that a lot of people act like living in those big cities is a necessity rather than the luxury that you've pointed out it really is.
I'll just say for brevity that people (especially young professionals) drastically underestimate 1) the amount of opportunities there are in other, smaller cities and 2) the quality of life that's possible on lower salaries in those cities.
In my opinion it's a trade off between quality of life vs. the opportunities that exist in big cities.
Of course, quality of life is subjective.
But, on the other hand, the vast majority don't. I'm sure there are certain people who really need to be there, but not everyone does.
[0] http://qz.com/729293/90-of-software-developers-work-outside-...