I saw a post from a long time player not too long ago, that finally got his tart mail. He quit a month later. A goal is a reason to keep going, a lack of a goal is a reason to stop.
A HNM ls friend camped every king every day for years, the moment he got his heca legs from nid he started missing camps and within a few months he was gone. Then a few months later he came back on a totally new character, with a clean slate of goals to work on.
I've been in shells with people who are really driven, play a lot and need goals and I've seen them get their long lusted after drop and quit soon after.
These things aren't in the game for the majority of players, these things are added to keep the achievers and hardcore players chugging along. These people need a goal and becasue they are hardcore they eat up every goal you put in-front of them, you need an ultra rare drop to keep them engaged.
If you don't do it, they will quit.
Again, it is fine if it's a cosmetic item but it needs to be rare and look good.