system
Given the following post, respond as if you're commenting on Reddit:
human
[Avengers Endgame] Why does running out of fuel in space matter?

Now this might be a two part question. I guess the important question is, does the fuel power the life support? If so then there is the answer, but as Tony stated, they ran out of fuel and they have been dead in the water since then. But if a space ship was traveling at max speed and the engines shut off, wouldn't it just continue to travel at that speed since there is no gravity to slow it down?
gpt
Their ship is not FTL. It uses that weird jump gate hex thing grid to travel. They could fly on inertia all they want, if they can't access the jump gate they won't get anywhere any time soon. Besides, as you can see, low fuel means powerplant goes down, and when it goes down, life support goes down, and when life support goes down, squishy meatbags go down.