you can understand their thinking though... google+1 is not for users, not really. its not like the facebook button where people click it to share stuff with their friends... the whole point of google+1 is to let google know that you think the page is worthy of being in their index. everything else is just fluff. so why put the button on a page if you dont want it boosted in the index? there's no point.
the only reason to put it on a noindexed page is if google spreads some of the benefit throughout the rest of the site. but is that the way it works? i dont think it is. a click only counts towards that specific URL.