The thing about this shot was I wasn't planning on taking this picture. I was interested in the architecture of the space they were standing in, but this young man openly engaged with me and invited me to take his picture. Since I am still relatively uncomfortable taking pictures of people, I make it a rule to never deny a request. I'm glad I did.
Not only does this gesture provide a positive and welcoming symbol -- but you have added context that gives the gesture added emphasis. The subject confronts us, the others do not. Because of this contrast, the gesture acquires more value.