Originally Posted by
Lethallin
It has to do with Japanese Ideology for what the DF is for.
In Japan, if you sign up for the DF, you're expected to know what you should be doing for a quick and easy clear. Using it for your first time is considered very rude, as you're imposing your inexperience on a bunch of random people that would rather just get it done. The Party Finder is for making and finding groups for learning and such.
I agree with that ideology for the PF vs DF, but since people in the west would rather take the easier route, the uses for both has practically flipped from the what the developer's intend.