And I quote:
"Inspired by a shared interest in the striking dress codes of various social groups, they have systematically documented numerous identities over the last 21 years."
"By registering their subjects in an identical framework, with similar poses and a strictly observed dress code, Versluis and Uyttenbroek provide an almost scientific, anthropological record of people’s attempts to distinguish themselves from others by assuming a group identity"
But the page I linked is full of commentary about the project and what the purpose is. You might not like the purpose, you might not think it has any merit, but it's clearly stated nonetheless if you're prepared to read it.