The point of
@Darkton93 imo wanted be that to show the appreciation through such purchases (sadly the only thing that seems to convince KT) can bring advantages in future: for example to buy a proper outfit for a not used unpopular character - as one of the "secondary" girls or a male - is not only a "vote" for that character in particular, but even for the other categories represented from it (outfits that aren't fetish, characters that aren't popular).
This doesn't mean that everyone should always buy everything that represent what they want see even if owned from characters that they don't use, this would be silly; however could be useful to to do it from time to time at least for a bunch of outfits (even just 1 or 2), a sort of "sacrifice" just for incentivate the people behind the game to do more of these outfits for the characters that we really want see (of course only if they are in the same league: to buy an outfit for Brad Wong has nothing to see with Kasumi). If people want see more outfits for Mila or Christie, is not so unreasonable to get an outfit from apparently upopular females as Lisa or Rachel. If people want see more outfits for Leon or Bayman, is not so unreasonable to get the outfit of Raidou or Ein or Brad from this pack.
I admit that for me to do it is higly easy finding fun in using all the characters (indeed for me would be more "convenient" to get the full packs), however as I stated nowadays I play very rarely the DoA5LR Xbox 360 version after getting the PC one, but again I bought a few Deception outfits just for this reason (same reasoning for the previous Fighter Force). The funny and sad thing is that I'm buying a bunch of single outfits in a version that I don't use more, while I'm not getting anything at all in the main PC version because the prices are too much high with their decision to release only mega packs (but I can understand their reasons behind it).