Except that in other languages the word order of sentences is different,
so the format items may not be used in the same order in a well-formed
sentence, or require a very awkward phrasing in the other language to
keep the same order as they would be used in English.
As someone who's done software internationalization before, I can assure
you that the problem is not nearly so easy to solve as is being
supposed, especially since internally the kernel was never designed for
internationalization from the beginning. Having done several such
retrofits, I can assure you they are utter hell. I can send interested
parties a document I wrote for a former employer detailing the
conversion problems I had with a program substantially less complicated
than the Linux kernel.
Probably the best argument against internationalizing kernel messages is
that currently they are standardized and understandable by all kernel
developers. While English is certainly not the native language of many
Linux users, imagine the difficulty Linux developers would have with
having to know and understand all of the languages used for Linux kernel
messages submitted in bug reports. It would also vastly complicate
system administration and monitoring software that needs to parse kernel
messages and would have to deal with all the different languages.