Because there's this Irishman in doubt...
1. Pets are endlessly interesting. Hardly a day goes by that they don't do something either confounding, confusing, frightening, flabbergasting, utterly adorable, incredibly endearing, or indescribably loving. Sometimes they can accomplish this all at once and it usually involves the formal presentation of a Dead Thing.
2. Pets provide unconditional love, especially when you are reading a book, it's raining outside and she REALLY HAS TO GO, any hour you are sleeping, almost anytime you are eating, whenever you are doing something involving a large number of very tiny pieces, or you are wrapping gifts. OK, so it's not on YOUR personal schedule. It's still LOVE.
3. Pets give you a from quarter to a half point toward being human when talking to People with Children. People with Children love their children, and hate the Undchilded for not sacrificing their lives, luxuries, hopes, dreams, and financial and mental stability on the alter of Childrearing. If they know you have pets, they know you have cleaned up poop, stayed up all night worrying about that cough, and been vomited on. Tthey won't immediately kill you from misdirected frustration. The more pets you have, the closer you are to being human. Larger pets count as larger point amounts. Goldfish barely count and ants don't count at all, so stop it.
4. Pets offer you chances for education in areas you'd never before considered, such as grooming, yard maintenance, carpet cleaning, assorted home repair, odor elimination, Creating the Perfect Litter Box, Identifying Half-Chewed Things In the Dark With Your Toes, and Post Digestion Detection.
5. Pets encourage you to improve your communication skills, since they don't understand most of what you say and certain of them couldn't really care anyway...which is very much like talking to people. However, you can curse, yell, talk babytalk, or sing to your pets and they will never tell anyone nor offer commentary of any kind.
6. Pets never offer critique on your weight, your manner of dress, your choice of music, television or movies, the length of your hair or toenails, how often you shower, your job, your hobbies, or how much garlic and onions you eat.
7. At least once a week, your Pet will do something (unconsiously or on purpose) so outrageously funny that you will laugh until you can't breath anymore. You might have to clean something up afterwards, but you will be weak from laughter and need some exercise by then. The more pets you have, the more opportunities you have for this kind of experience. Also, they won't mind too much that you laughed.
8. The Average Pet has a very short memory. They won't remember you were an asshole yesterday, that you forgot their birthday, that you cry over certain TV commercials, that you drink out of the container, or that you occasionally lie. They won't tell anyone your masturbatory habits, your middle name, or where your porn is stashed. They will never reveal what you said about your boss, your mother, your mother in law, or that jerk who lives next door. They are the perfect confidants.
9. Pets are never too busy to listen to you, to go for a walk, or to share a meal. They always like to sleep in and can usually be persuaded to share the blankets. They are happy to see you, even if they are very good at hiding it. They think you are the most interesting, wonderful, fabulous, glorious creature on the face of the earth (in the case of cats, next to themselves). To own a dog is to be nigh unto a god. To be with a cat is to share a comfy chair with a god. There's not much to be said for goldfish.
10. Pets will not break your heart as long as they live. Ever.