Henri Cartier-Bresson was a humanist. He cared about people. He was curious about people, about who they were, about how they lived — about what brought them joy, about what made them suffer, about how they prayed, about their culture, about how they were affected by historical events, etc. That's why he traveled to India, to the US, to China, to the USSR, to Ireland, to Japan, to England, etc.
He wanted to be a witness — and had the means to —, and invented Magnum so that others could do the same. That, to him, was what photography was about. About humanity, about being a witness to our human condition.
This is a great quote, from a 1986 interview:
"During the three years when I lived in the Far East, I did not see my pictures often, except on occasion, when they were published in magazines. At the time, I was absorbed by life."
Or this one:
"I was never without my camera; it was always tied to my wrist. My gaze constantly scanned life. This is what made me feel close to Proust when, towards the end of À la recherche du temps perdu, he writes 'Real life, life at last laid bare and illuminated... is literature.' For me that was photography."
Not only is putting any formal or esthetic concern above that a misunderstanding of what photography meant to him, I believe he would have found it insulting.