[Fluff] Why don't people clear the zombie outbreak stages when they're either in or they finish ZL?

I heard from a friend who actually finished ZL that a lot of people don't finish the Zombie Outbreak stages and they're either in or have finished ZL. I feel that is a huge miss opportunity because they grant you 4-5k cat food in total if you finished all of them.

I finished all the ones I can confidently beat (up to CotC Chapter 2, which I only beat four outbreak stages as of making this post), mostly carried by Salvation's Daughter Lunacia, which actually makes them fun imo than a slog people think they are.

If they think Outbreak stages are slots or zombies are unfair or something, then I don't get how they're even past Musashi, let alone in or finish with ZL. I may sound stupid or something, but the idea of people THAT late into the game without the outbreaks completed genuinely confuses me.