Rabbits are plentiful and easy to catch, but they are not nutritionally complete. If you eat only rabbits, you'll go crazy and die

>If there are enough rabbits, the people eat till their stomachs are distended; but no matter how much they eat they feel unsatisfied.

https://en.wikipedia.org/wiki/Protein_poisoning

Back in UK history there were paid rabbit hunters, who'd roam a farmer's land hunting rabbits. They ate a lot of rabbit. It turns out that rabbit meat is not nutritionally complete and some of them died.

https://fourtallpalms.com/why-rabbit-meat-is-not-the-best-su...