Simply because there misinformed about what pagerank is... Unless there selling links then its your job to tell them that there wrong.
I personally dont see it as my responsibility to tell them as i think they would take offence. If i sell a dress to a fat woman then tell her she shouldn't concern herslf with ever wearing it as shes too fat for it, id get told to mind my own business right? PR is not mine, so i cant tell anyone they shouldn't look for it, they will find it anyway, some place else.
If you build lots of backlinks and you add freah content in your site, then you will get both the PR and ranking