If you crash, it hurts!
I think I’ll just have the player wanting to get to the goal post.
In order to do that he will have to refill the ship’s fuel tanks and in order to do that, he will have to shoot some things that provide fuel and would try to escape the ship’s path otherwise. If the player doesn’t manage to catch enough of those things he’ll eventually run out of fuel and the ship will crash (or have to make an emergency landing).
There can be different enemy types. The simple ones are just trying to escape. More “hostile” ones will slow down the player or otherwise cause fuel depletion to put the player under distress.
Or possibly to fuel pods (or whatever they are) are attractive to other beings as well, so the player has to defend them against getting snatched away.