Chinese Names

Why do Chinese people assume the name of westerners when talking to a westerner?

'cause they think it makes them fit in, without realizing that they have a massive lack of cultural context when choosing their names
I've met a guy here (Beijing) who chose his "American name" as Satan, and another as Adolf Hitler. They were both adamant that it was their name, and they wouldn't change it. They didn't understand how much of an ass they were making of themselves.