The oldest sibling learns early that pressure can come with no instructions. Figuring it out anyway is a real skill.

The eldest gets the responsibility before anyone has worked out the rules. There is no earlier version of you to watch, nobody who already made the mistakes, and the expectations usually arrive without being said out loud. Working it out from scratch is a genuine skill, and harder than it looks from below.

Try naming one expectation you have been meeting without ever being asked, and check whether it is actually required. Ask a parent directly what they expect, since the stated version is often smaller than the one in your head. Find somebody older outside the family who has done this, because borrowed instructions beat none.