The obvious answer is the one posting may not have been aware it was a Bible quote. If you're talking about a case where the Bible quote and reference is given, then it might just be an oversite. It's easy to cut and paste an EGW quote, and someone could do that without even thinking that it's a Bible quote. Or that might already have it in front of them, and not want to make the effort to find an on-line Bible to quote from (quite often EGW quotes from a translation which is no longer commonly used, so just quoting it straight from what she wrote might not make it clear what translation was being used).