Not sure that the format of a site necessarily defines the demographic, it's just a different user interface which might be easier to use, might not be, might be your thing, might not be, regardless of age, gender or interest.
The reason for posting is purely that the steem ecosystem is evolving and that developments are occurring that may well have an influence on steemit, for example, by incorporating the forums as a "Community Pages" element within steemit - or linked from steemit.
I guess part of the issue is that the sites are sitting on top of the steem blockchain, if you like, so that steemit is solely an interface for that, all our activity on here is visible through alternative means, so it will be interesting to see how the interfaces evolve - we are likely, I suspect, to end up with a number of different platforms all providing access to the steem blockchain, users will be able to interact across platform and therefore choose the interface that works for them.