Yes, it would feel restrictive at first, but it would force someone to build a solution for allowing documents to be shared company-wide.
You guessed it, this rant is about the stupidity of restricting access to documents, not the woes of attachments. Well, it's both really. I shouldn't need to receive extra copies of one attachment just because my project manager includes me on an email asking others to provide feedback. But what else can she do? If she puts the document on a shared drive or document repository, access control will prevennt some people from getting to it. So, everyone continues to email attachments. What a waste.
EDIT: I vote we name our installation of SharePoint "BlockPoint" to highlight the way we're limiting its functionality.