Understandable. Actually even I'm glad you added this option, and truth be told, it makes more sense because SBD fulfills the original purpose of the site: direct payment reward for contribution.
Accumulating SP is a noble idea, definitely, but not viable for mass adoption. I guess the fact the community asked you for supporting SBD is another indicator for it.
Then again, don't take it as criticism - I rather tried highlighting both sides of the "coin".