Apart from several and diverse individual needs to do this people may have, it occurs to me that this shortcoming is also holding Pages from achieving its best potential. I really need this badly for a third app I have on the forums; however, I run IPB for my forums, blogs, etc (still 3.4 and waiting on this precisely so I can upgrade), then I run a directory on Joomla (using SobiPro), and a splash page on Wordpress matching the look of the Joomla one, but giving me a bit more flexibility for SEO purposes. (Maybe a bit overkill when my forums subdomain cannibalize any SEO attempts as it is the most popular one, but never mind that)
My wish is not having to run a website that consists of 3 completely different pieces of software any longer, and I'd be happy happy to do the whole lot with IPS (and maybe move all just to the top domain). However, while I'm sure that you must be able to build a directory using Pages (or maybe Pages and other apps too), you cannot have a directory where users can search by attributes if you cannot search custom fields (yes, you have tags, but I think it's not quite the same). So, I really hope this functionality is back with IPS 4.3.