Not everyone speaks English.
Not everyone writes using Latin characters.
Unfortunately up until a couple of days ago there was no way to have a domain name 100% in a character set other than Latin. Sure, you could get special characters in the domain, but not in the extension ie. the part on the left of the “.” could use special characters, but the bit on the right couldn’t. So you could register a .com or a .eu with special characters in it, but the actual domain extension was still in ASCII.

ICANN has announced that the first non-Latin domain extensions are now online. You can read more about it on the ICANN blog