Signature doesn't appear in first post

Many community users have a signature block that is appended automatically to a message.

Unfortunately, the initial post in a new topic does not include a signature.  Some like to indicate the version of the product (e.g. MicroStation CONNECT Update 17) in their signature.  When the signature is missing from the post, we're left wondering what product the OP is using.

Is there a reason why the signature is not included automatically with a new post?