I can't speak for everyone, but when I went to Bolivia with a medical team in 2000 as a high-schooler my life was changed. I don't keep in contact with anyone from those days, but the experience made me a better, more empathetic person, and I better recognize my privilege as an American.

Am I perfect? No. But it still gave me a different perspective on the world than my experiences in the marching band as a middle-class white Texan kid. I went into it brainwashed as a hard-core Republican. That didn't change in my few weeks in Bolivia, but the impressions it left on me were a large part of how I came to re-evaluate my social, spiritual, and political beliefs in college.