...mainly because I haven't read them yet. And don't like being reminded of my slackness - almost all are on my longer term TBRs.
I just updated about 20 challenges I first did around 10 months ago and these books kept reappearing, without the satisfaction of getting to check them off.
I'm really keen to see what percentage of list challengers have read these pesky works. I'll probably read most of them eventually, even if just to make them "go away" (I'm only partially joking). You also might have noticed that I thoughtfully used less commonly seen icons to minimise the tedium.