Do you think a dog or cat enjoys having a 4-legged companion or would be fine without one?

We have two dogs. Since they sit next to each other so closely on the sofa, have chasing matches around the house sometimes and fake argue over toys I think they are very fond of one another. I don’t know how they’d be alone without an “s/o.” Did you buy your pets in two’s and , if so, did you do it for them and believe they like having a friend?