Every experience he has ever had with hero's has been bad. Hero's hurt the people they're supposed to protect. They crave the money it brings or the fame that comes their way. Hero's are selfish and could care less about people like him. People who really need a hero, someone to save them, but the hero's never come. But Izuku wants to be a hero to help people smile. If this green bean can somehow shine as bright as the sun for someone like Toya, then he can only imagine what he can do for others.