Living in Latin America where the Latino culture of work-to-live is in contrast to the American idea of living-to-work, the most common reason I hear is just to live a more relaxed lifestyle.
More Americans choose to live abroad for financial reasons.
Globalization has allowed more people to pursue international careers that are less dependent on location, further allowing them to live abroad.
The pros and cons of living abroad are going to depend on where you go as well but there are some common themes I hear from other expats.
Most expats choose to relocate to a country with a lower cost of living, Latin America being one of the top destinations.
My biggest complaint here in Colombia is the informal nature of the culture. Public services may not work as well as you would like them in your destination abroad.