That is a good point. The issue I see with Facebook is that it is a “surveillance company” by design. It was developed for data mining. Steemit is transparent and can be mined for surveillance, but I don’t think that was the purpose for its development so it is not as “user friendly” to data miners as Facebook.
The other point is that while some Steemians use this as another Facebook and post everything about themselves, many more remain hidden from view and don’t reveal personal information while commenting and posting. Therefore profile mining does not easily produce specific results.