Well many parents get the pets for the kids, but we end up having to look after the little blighters ourselves! We have 2 cats that we got when the kids were younger, and now the kids have left home we still have them. They are 13.5 and 11. They may well live another 10 years!
I love the little fluffy munchkins, and they give lots of love and cuddles, and I don't regret getting them, but they can be a royal PITA! 
When the one pees in the litter, she misses it half the time, and I have to scrub the kitchen floor every day, they vomit on the carpet at LEAST once a week, and they bang the hall door to be fed at 6am to 7am most mornings, waking us up. Which is bearable in the week, but a PITA at the weekends!
In addition, they costs several 100 pound a year each for preventative vet care/flea drops/worming tabs etc, and 300-400 pounds a year or more for food, (plus lots more in pet insurance or high vet bills if you don' have it!) AND they run around my feet tripping me up sometimes when I am doing housework or putting washing out, which I find frustrating and annoying, as they have almost sent me flying many times!
Cats are easy pets to look after, but if you are buying one (or 2) for pets for the kids, it's important to remember that they last a LONG time, and will be living for up to 10 years after your kids leave home.
Same for dogs really. You really do need to think it through before you get pets, especially ones that live more than 4 or 5 years.
Also hate - with a passion - birds being caged, or any animal actually. When we had a rabbit many years ago, we had a 12 x 10 foot run for him, as well as his hutch, and for at least 4 hours a day, we would let him run around the garden, (which was safely fenced off from the outside world.)