For a more "basic" rendition:
Men are naturally competitive (and that's why men get the women to their side) while women are naturally supportive (and that's why women get the men on their side ). We all know that computing is unmistakably for men, not that women are excluded, but simply women are, shall we say, "not hard-wired to do computing". So what comes natural to grids wanting to get as many crunchers as they can? Do I even need to answer that question? Ok, I have to: reasons, excuses, claims, the hell even a bluff who cares -- as long as there is a chance to compete, men will go there. Ever wondered the raison d'être of badges, points, runtimes, need not wonder now.

For a more "intellectual" rendition:
One thing is, we can have both the points and crunching-for-the-science at the same time, without interfering with each other. I get the feeling that sometimes some people view the crunching-for-the-science as necessarily done best if no points are involved, and that having a pointsSystem in place necessarily results in not doing the best to serve the crunching-for-the-science part. The mindset there is fixed as an "exclusive-OR". The reality is more like how an "as-long-as_then-add" mindset views things: as long as the pointsSystem do not interfere with the crunching-for-the-science, we can have both. I have yet to see proof that the pointsSystem interferes with crunching-for-the-science; on the contrary, I see clearly observable evidence that points (along with badges, runtimes, etc) makes an otherwise boring and faceless activity of crunching -- a true and enjoyable part of living in the 21st-century.
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