time sinks.
they are there to keep you in for a lengthy period of time.
to do that you need goals of archievement.
one goal would be to hold a nice/class defining item.
now lets take a look at how ao is designed:
we have shops that are basically useless forcing you into spending hours camping the damn terminal until clicksaver came out.
you have "uniques" that help keeping the annual income of mmrpgs higher then some countries (hello ebay).
you have the saving grace of rifles, pistols and assault rifles on random boss mobs in team missions only.
it is just a lazy way to keep people going.
what annoys me about this is that the average player has about zero chance of aquiring sexy items unless he joins an über guild routinely camping the spawns.