When my middle sister (now 19) was born she was born at only 27 weeks gestation and was in hospital for the first year of her life. My parents didn't have any pets then (only me
) but if they did I can see they would pretty much have had to rehome them - something like that just uses up all your resources and then some, my dad lost his job during that time too, I'd not feel able to give an animal enough care and love, let alone the finances - even I had to be shipped off to be looked after by my grandparents!
Obviously not everyone's in a crisis situation like that but they wouldn't always think or feel able to tell you about it so I'm always careful to keep my judgements to myself... even when I'm pretty sure that they're just full of cr*p and were never fit to own a cat in the first place.