Why are there cats everywhere?

Cats have been part of medina life for centuries. They keep the rat and mouse population down in a city built on narrow streets and open drains. They're tolerated, fed scraps by shopkeepers and residents, and largely left to roam. Most are semi-feral — friendly enough to approach but not domesticated. Some have eye infections or are underfed. A handful of cat food and a few dirhams' worth of eye drops from any pharmacy will be much appreciated.