Pokemon Snap is a game about taking pictures of pokemon, which should be fairly obvious from the title.
You just kind of go around taking photos, getting them graded, and getting points for them.
Eventually, you'll open up 'challenge scores', one for each level.
Now, what do you get for exceeding the challenge score for all of the levels?
Nothing! Absolutely nothing!
Other than the satisfaction of knowing that you've bested the last challenge the game could throw at you, which counts for something, right?