Persistent universe.
You're playing a game in the same universe as every other player, the clock never stops ticking. It's not ideal but FD made it clear before the game was launched there'd be no offline single player game because the whole game can't run on a normal PC or the game wasn't finished yet or something or other.
If you're not having fun playing the game. Stop playing it.
You don't get to just say "persistent universe" as if that is an explanation in itself. It's not an explanation or a justification.
I don't CARE if the game world clock keeps ticking when I am offline. That's fine. But whyyyyyyy do MY missions, which
only I am responsible for, which DO NOT EXIST for anyone else in the entire (persistent!) universe, which have no effect on ANYONE but me; why must they have timers which tick down when I am NOT PLAYING?
My ship doesn't consume fuel when I'm not playing. My shields don't recharge when I'm not playing. If I have an Unknown Artifact in my cargo hold, the cargo hold doesn't corrode while i am not playing. If I have an assassination mission to kill a particular NPC, that NPC DOES NOT EXIST when i am not playing. He doesn't go flying around the galaxy doing his thing independent of me, and some random CMDR can't stumble across him and kill my target before I find him. If I have a mission to go retrieve a black box over at some random system, I am the only one who can do it, because the black box does not exist, and will not exist, until I personally go and look for it. No one else can find it. Ever. And if a pirate chases me away before I can scoop it up, or I crash into the canister and blow it up, I can fly around for a while and suddenly it will re-spawn surrounded by a whole new set of different random debris and in a different location and under different circumstances.
But if I accept a delivery mission on a Wednesday, and then sign off from the game until a Friday, it's "Mission Failed" because Persistent Universe.
Yeah, OK.