Because they don't want visitors false-flagging them. Most people would wear costumes just for the fun of cosplay, but Disney clearly doesn't want to deal with bag snatchers, predators and unfunny pranksters using their actors and the other costumed guests as cover.
Security Officer: We have a report of a 300 pound male with a beard dressed as Snow White who was caught taking pictures of little boys in the bathroom
Control: Can you be more specific, there’s hundreds of fat bearded Snow Whites
Because they don't want visitors false-flagging them. Most people would wear costumes just for the fun of cosplay, but Disney clearly doesn't want to deal with bag snatchers, predators and unfunny pranksters using their actors and the other costumed guests as cover.
Security Officer: We have a report of a 300 pound male with a beard dressed as Snow White who was caught taking pictures of little boys in the bathroom
Control: Can you be more specific, there’s hundreds of fat bearded Snow Whites