What's all the fuss about? The adage goes something like, "if you're not heading to the beach, leave the flip-flops at home." People expect men to wear real shoes (shoes that cover gangly toes). Not to mention, women aren't big fans of guys in thong sandals. Men with visible feet while running about town is a social stigma that obviously isn't concerning to the frat bros of the world.
And besides the social stigma, there are even schools and workplaces banning them due to safety and hygiene issues due to exposed toes and their prevalence to slip of, causing accidents.