It gives them a predatory advantage.
What does it mean when my cat's eyes are dilated?
6 Common Eye Problems in Cats: Causes, Symptoms, Treatment & Prevention
Pets, Pets, Pets - Massapequa Post
The World Through the Feline Eyes
Revealed: why animals' pupils come in different shapes and sizes
Why do cats and snakes have slits for pupils? - BBC Science Focus Magazine
Predators have vertical slits for pupils, while prey have 'letterbox' shaped holes
Why Cats Have Vertical Eye Pupils
Guide to what different shaped pupils do as well as the animals which have them. : r/coolguides
Why Do Cats Have Vertical Pupils?
Why are my cat's eyes dilated? - Vet Help Direct
Why Do Cats' Pupils Get Big? - Cat Box Classics
Study Reveals Astonishing Reason Why Cats Have Vertical Pupils!
Why Do Cats' Eyes Dilate Everything You Need to Know
Why Do Cats Have Vertical Pupils? · Falls Village Vet Hospital