Just that, really :)
I'll go first: we have two bitches, an 8yo parson russell terrier (from breeder) and a 17month old border terrier cross (from rescue), and the reason we have them is that I cannot imagine living without an animal.
I love the relationship between us. I feel privileged to be allowed to share their lives. They are affectionate, funny, cute and stubborn. They enrich our lives in so many ways - I love that we are outside so much more because of them, that we are so much more aware of nature and the changing seasons, that we don't mind going out in the rain (because of course we have the right gear!).
I love that ds is growing up with them, and I think it makes him much more aware of animals in general, and (I hope) kinder towards all of them because of it.
Um, I'm sure there are more, but those are the ones that spring to mind!
So come and tell me what dog(s) you have and why you have them :)