Why is there an engine per locale?

[Kris Rasmussen]

Can anyone explain to me why tapestry pools engines by locale? I beleive I 
looked into this a year or two ago but I can't seem to remember what I found 
and I need to know it again ;). From what I remember, all the templates are 
fetched from the same pool with the locale included in their multi key so I 
don't beleive it has anything to do with templating. Is it because property 
language files are stored somewhere in the engine?
 
Thanks,
Kris