Various reasons. They repro too fast if not sterilised....and in
communities where the strays are all sterilised (by care givers), u
just need 1 irresponsible cat owner to dump a cat/a couple of
kittens and it can start off the reproduction again. Then there are
those wild roaming males who roam across wide territories and mate
with any female on heat.
That's why we need a nation-wide plan to stop the population growth
- must all sterilise together within a few months mah, but govt
don't support.