Alot of what goes into building a sub is classified, so even the non-sensitive parts of some aspects get put in the same category, ie. all blueprints, manuals, procedures, etc...
It's kind of a shotgun approach but the machine that makes the machine that does the sensitive stuff could be something we don't want someone else to get.
Basically technology is power, hope that explains a little of the silence. Plus if people aren't sure what is and isn't "secret" they generally fail safe and assume it is.