system
Given the following post, respond as if you're commenting on Reddit:
human
Why/when did someone decide it was indecent for genitals/boobies to be exposed?
gpt
Cultural attitudes towards "decency" vary greatly by place and time, but assuming you are talking about the United States: it can be traced to the Puritan settlers, who had a huge influence on the colonies and the country they would become. 

Over time attitudes have changed, but law changes much more slowly. Note that simple nudity is not considered indecent (by law) in every jurisdiction. In California, for example, public nudity is not technically illegal, as a result of a California Supreme Court ruling. 

European countries tend to be much more relaxed about nudity. They don't walk around naked, but they also don't freak out over naked bodies in appropriate situations. There is nudity in advertising and on television, and in public in places like the beach.