an attached doc/x document file could be maliciously scripted and can be indexed by search engines, so it's not suggested to have that extensions allowed.
Oh bullcrap, you can still rename the file and post it. Nothing is being prevented, it just makes it a pain in the ass. It's 2015 and this is a forum for engineers and engineering aficionados, we ought to be smart enough to decide for ourselves what we're willing to open.
Speaking of which, anybody want to download and run the attached (with no contest by the forum software, I might add) shell script? No need to rename, just
curl URL | sh