It would be selfish to not put the pet down if it's suffering. Pet's can't speak, you have to speak for them. And you better make the right decision. (In this case, putting it down would be the best decision.)

They definitely don't want to die though.

It sounds like you are only addressing a scenario where the decision is clear and yes, I agree pet owners tend to extend their suffering for the reasons you described, but what about the grey area? What about a scenario when an animal is suffering to some degree (and perhaps not indefinitely, there often is a hope of recovery) but you still aren't sure if it's a life worth to live or not?

I would put it down if its life could be saved but the procedure is expensive. I would put it down if it were completely healthy and i didntwant it anymore. No grey area

As a lover of animals, and more then likely I will have a future working with animals. If I had euthanize a dog or any animal due to an infection or something I knew they would ultimately die from, I'd have to say yes for the sake of putting it out of it's own misery. Something unnecessary I am completely against.

Life is full of tough decisions. That's what being a responsible adult is about. You have to make an informed descision based on what your vet recommends. What's best for your pet is not always what's best for you or what makes you feel good.

We do sometimes "put" people down such as my grandfather who had multiple problems (alzheimer's, parkinson's, and probably a few other things). Well one day he lost the ability to swallow. My mom (daughter) could have decided along with her siblings to stick a feeder down his throat or hook an IV to keep him alive. However, they decided to let him die. When you lose the ability to swallow that might be a sign that it is your time. There are numerous other cases where family members "pull" the plug like those who suffer brain damage, coma, etc..  I believe keeping someone alive purely on machines with no chance of recover is unethical.  The ethical thing to do is let the person die.

I had put down my beloved cat. It is painful to see them suffering,as much as i wanted to hold onto her for longer, sometimes it is the right thing to do.

My family put down our oldest dog earlier this year. He was almost 16, was completely blind and deaf, and also had cancer (I believe it was prostate). We had him on antibiotics to help with his bladder for a few months but it got worse and worse. He hardly moved around anymore and when he did he'd be constantly walking into walls and had no sense of direction.

I remember the day we put him down quite well. There was just a strong sense of sadness in the house. We fed him a big juicy steak for his last meal before taking him to get put down. Such a sad experience.