[Suicide Junkie]

For example, I give orders to a planet to transfer fighters to a carrier. Well, the planet shows a "drop cargo" order, but the carrier's orders show nothing.

Well, in this case, it is because the carrier isn't doing anything.
The planet is sending the fighters. You could also order the carrier to load fighters, but that would be redundant.

If you're going to have the carrier move off to engage the enemy later that turn, you'll want to have it actively load instead of passively having the cargo dropped to it.