Some people think it is cool to use a fake name.
They either want it because their real name is dull, gets misspelled often, or because it is longer than their fancy name. Crime Criminals often use fake identities - and cryptography. This cannot be prevented, so we have to live with it. But I will never give up free speech and cryptography just to shut up a few criminals. A pseudonym might be shorter than your realname - but everyone else might use it, too.