Actually it is a important feature for small sized details in a Image. it is on how many Pixles dots you will have on a surface of one Inch PPi . the 72 dpi is the Ideal resolution for web as it keeps the size low . But lets look at at this

" Generally, a 600 DPI scan is the best image resolution and pixel count for paper photographs. High resolutions above 600 DPI are better suited for professional archive work due to the longer scan time and larger storage requirements. "

" 2400, 3200 and 4800 dpi — are intended for capturing really small and highly detailed sources like film negatives and slides. "

you can't take a render that was made with 72Dpi into a photo app expecting to bet a better quality by increasing the Dpi to 300. If Poser 12 is having the issue not being able increasing the Px per Inch and just render web based resolution then you might be better off with prior Poser releases to have Pro results. sure takes a little longer, but quality takes it's time.