It is not a fair bet to traders because as you say it is a "forced" position, traders have to lock their steem and this is the worst thing for a speculators. There is no way to speculate on steem without getting hit by the inflation which is why traders are not buying it.
Fair is a loaded word. I was using it in a sort of specialized but value-neutral way to mean that it isn't being inflated/diluted away the liquid STEEM is. With a position in SP, if the platform gains in value as a whole (market cap), you investment will gain in value as well. That is not true of STEEM, where you also have to beat inflation (not impossible that this ever happens, especially short term, but certainly a lot harder).
I agree that locking it up makes this a less attractive play for many traders. One of the real obstacles that Steem has always faced is being structurally investor-unfriendly. This is especially true because, even though as SP investor you have voting rights, the SP is so concentrated with insiders that the voting rights to a new investor, even a fairly large one, are all but meaningless.