When you are managing people that manage other people, so not everyone _direct_ly reports to you.

Reporting hierarchy is there for a good reason. If you report to multiple people, you're the one that's going to have a bad time when they're not aligned with each other, each trying to give you a different list of priorities.

Why don't they know what's important and what's not?

In a larger organization, "knowing what's important and what's not" at all times can be practically a full time job in and of itself. A lot of engineering teams like to protect individual developers from meetings and conference calls so they can focus on development, but that necessarily means developers will be missing context.

Why does it feel jarring?

I think it's because it implies that their job is to report to you -like you're really the brains of the operation rather than just in a different role