why do dogs get put down screw humans let dogs rule

Hey. I'm rly sorry... My dog Sally had to get put down because one morning she woke up and her two back legs were paralysed. She was a border collie, my sister, one of my best friends and my other dogs (my other best friend) sister. It's so sad... But just think that the vets only do what's best for the animal. So I guess if that means putting them down... It doesn't make it any more easier though. Feel free to talk to me about it whenever you want. My thoughts are with you.