Diadem's kinda annoying..

[Selli]

Most pugs will pass i210 if it's not for their main (which is usually the class they go on). Every once in a while, you will see a couple people who disagree and say they will roll anyway, and unless they change their mind, people will just leave. It's not worth their time if there's a chance they might not get their loot.

How would you feel, OP, if you lost a Ninja chest piece with VIT, DEX, CRIT, DET, and SKSPD to a healer who didn't even have NIN unlocked? You'd probably be pretty pissed. Which is why people now express common courtesy in this content, especially since you can't replace those who leave, so their requests about the i210 are taken seriously.