That's right, the extra effort isn't the only cost, the spreading of SP around will also diminish the benefits. But people so often don't think  more than one step ahead with anything, or to the secondary outcomes after a primary outcome. This is the result of humans short lifespans and is called 'Time Preference' in Austrian economics. The effect it has on behaviour here is unquestionable, and that is why the defaults need to be changed.

BTW, I voted for your witness with @l0k1, keep up the good work :)