It is extremely stressful to move to a foreign country where you won't speak the language correctly, you don't family and friends and the social and psychological safety net you're used to, and you don't know the local customs, AND you'll be a second-class person even if you do somehow manage to get legal papers (which are a huge source of stress in and of themselves).
That's why most people that do are either young people (more adaptable) or families under economic hardship.
In my case, my girlfriend won't consider moving to the U.S., and I won't consider moving without legal papers, which means a H1B visa for me, or moving to Canada and starting the long citizenship process.
That's why many smart people will accept lower wages in order to stay with their families and friends and environment.
I know firsthand what it means to emigrate, one of my brothers is living in the United Arab Emirates and tries to convince me to emigrate very often (I'd instantly double or triple my salary, plus the UAE are much cheaper than Uruguay), and I have family in Austria and Canada. All three countries are great (I like Austria the most, but I don't speak much German), but all of them represent all the challenges outlined above.