Why do casual players seem entitled to cosmetic items added in game?

[BigCheez]

Okay but you literally have no valid reasons for your opinion.

All content should have rewards. Cosmetics are a great way to add rewards to content without making the activity mandatory for character progression.

It's actually you who has no reasoning to back their argument. It's literally just a case of "I want the rewards but I don't want to do the content therefore the reward should not be locked behind the content", i.e. entitlement.