I know that through all sorts of tricks and past experience you can almost (and sometimes definitely can) pick hotels even when bidding through Priceline. However, since by the very nature of bidding Priceline could give you a completely different hotel and you'd have no recourse, I'd say you are showing no loyalty to the chain, and these programs, like SPG, are all loyalty programs. Hence I don't believe they should earn credit.
Now I maybe more than anyone would have most to gain if THEY did provide credit -- I would have been platinum a lot quicker since I still use Priceline for most of my leisure stays. But I understand Priceline's limitations and am happy that Starwood has gone on record to offer other benefits (the upgrades, etc) for all rates. But I do not think Starpoints/stay credit fits the bill.
Even Wyndham, one of the few chains that early on said that Priceline stays would be equivalent to any other stay, recently changed their policy to give all benefits EXCEPT the airline miles (they don't have a stay based program, so that doesn't apply), just like Starwood.
Just my respectful $.02