[throwaway66666]

Problem with alphanumeric, is you have people from foreign countries who do not even have an english keyboard installed on their phone. Default is probably their native language and they do not care to add a secondary or switch.

Numeric values solve that problem.

edit: drunk typing

[kalleboo]

Is that a thing? Domain names, email addresses, passwords all tend to require the latin character set. Here in Japan I can't remember seeing a single site that uses kanji passwords.