Now, if I'm mistaken about any of this, someone please let me know, but I think I can answer most of your questions in a pretty straightforward manner.

Cryptocurrencies like STEEM gain their value from CPU-time, reminiscent of SETI@Home from the 90's; with a complex calculation that could take millions of years for one computer to process, but can be broken into smaller pieces, the time spent calculating each piece of the greater calculation holds value relative to both time, and the invested capital value traded for and with it.

With STEEM as the base token, SBD acting as a balance against the US Dollar, and STEEM Power serving as an investment of voting toward the community value of a given post, by creating or curating content you are essentially moving the social-capital half of the market, which merits value in the ForEx-capital half of the market.