>>281746477
He has the same 1 personality trait every Kimetsu character has which is optimism in the face of impossible odds. Hand cut off? Keep smiling. Blind in one eye? Keep going. It's the same reason people like Rengoku, or hell even Tanjiro. KnY is about indomitability of the human spirit when fighting quite literally indomitable enemies who automatically recover from any injury. There's only so many ways you can show this: guy shows his optimism by remaining stoic, guy shows his optimism by smiling, guy shows his optimism by encouraging others, etc.