Why are so many "adult" animated shows ugly as fucking sin?

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Have you seen Scavengers Reign? That's a recent cartoon for adults that has incredible animation. It's also a sci-fi drama, not a comedy. Shows like these do seem to be a rarity, though. Probably because cartoons are harder to market to adults, so they don't usually get the budgets they would need for higher quality animation.
The owls are not what they seem.