Counterpoint...
I grew up and lived in Chicago for most of my adult life. I moved to the Bay Area in 2013. My main reasons were weather, crime, and jobs.
For some people, living with gray skies half the year with not-infrequent temperatures below zero or above 100 takes its toll. Also, the violent crime rate has gone through the roof in recent years, even in generally good neighborhoods.
On the jobs front, I'm in marketing and a more technical marketer at that. The job options in Chicago were largely unappealing, but more importantly was the major difference in culture. There are obviously exceptions, but Chicago seems to have a much more "conservative" corporate culture on the average. This means less competitive pay, 2 weeks of PTO, 2 weeks paternity (if that), stricter 8 or 9am start times, less free on-premise food, fewer perks overall, less competitive benefits, etc. Again, you can find exceptions, and large tech companies tend to have offices there as it is a hub (particularly for media companies like Google). But on the balance, due to the extreme concentration out here, it seems many Bay Area companies are forced to up their game and be much more in favor of the employee with regards to comp, perks, culture and benefits if they want to be competitive with the local giants.
I get very sad when I think about the cost of housing out here, but TBH, I'm not sure I could go back. Whenever I get off the return flight from a trip home and step out the doors at SFO, all of the color, sunshine etc. makes things look like technicolor compared to the ugly red brick, gray skies and black slush of Chicago.
Don't get me wrong--it will always have a place in my heart and I dearly love many things there. But depending on your priorities, in some cases there is no competition if you can afford enough to make it manageable.