There is a reason this occurs.

Generally, fathers are the most attached to the pet out of all of the family, due to various reasons (puppy love, high obedience, petting, etc.). However, fathers are also keen to know that dogs do not last a human's life time.

What is given can be taken away. And when that dog passes away, the father will be the most heartbroken out of the family, due to being the most attached. Fathers know this, and dread the day their dog leaves them should they have a dog.

This perfectly describes my dad. My father is the biggest sucker for animals---Even being allergic to dogs, he just can't bring himself to turn one away. The first time I'd ever seen him shed a tear, he was sobbing rivers over coming inside from doing yardwork to find our dog Bear (beautiful black lab/border collie mix.) dead at age 15 laying against his side of the bed instead of sleeping against the front door waiting for him to come in like he'd done his entire life.

Him when my sister asks if she can bring home the dog she found someone giving away: "No more dogs, we already have too fucking many animals"

Him when my sister disobeys him and drives 100 miles to get a designer shih-poo mix for free: "Find someone to take it by the end of the week or I'm sending it to the pound"

Him two weeks later after my sister makes zero effort to find anyone: (Sitting on his chair watching TV with the dog in his lap, scratching behind its ears)

Him a decade later when the dog has been 90% blind in both eyes for 5 years and isn't doing so well: (Gets visibly sad while pointing out the possibility of him dying soon)

Even now that she's 29 with a kid of her own living at home to save on rent, does she stop that shit? No, no she doesn't. Instead, her fucking 10 year old now knows that she can have whatever dog/cat she wants so long as she brings it home without telling him.