Because this could only happen in Iowa, which is first up - and where a tiny percentage of the people decide who wins these stupid caucuses. Because Iowa has an outsized influence, this straw poll is considered a necessary show of strength.
But it's all a bunch of smoke. Iowa's Caucus ends up having very little impact, and the Ames Straw poll having little impact on the Caucus. Last time Bachmann won the straw poll, but was about dead last in the Caucus. But the Iowa GOP made their money!!
IA seems ready made for the third Bush and HRC.