Well if you're peeking before you vote, then there's a good chance your vote is biased by the fore knowledge. This effect affects even the most intellectually-honest scientists, which is why double-blind studies, where neither the tester nor the testee knows whether or not the proverbial "pill" is a placebo, are the gold standard.
This issue comes up in the media every couple years during elections, when results are posted before everyone's voted -- not a good way to do it!
After you vote peeking doesn't matter.
So it's good this board's polling system has a separate "show results" action.