I'm very happily single and not looking for a LTR and I have a dog.
My dog is my companion, I consider him a friend, a partner. My relationship with him is a combination of companion, partner, parent child. He will never be my life partner, he's a dog and I treat him as such. To treat him as other then a dog would be to do him a grave injustice.
I love animals, and enjoy having a dog. I love having someone to come home to, and someone to take care of. While I do have good friends that are human I enjoy coming home to just my dog. That's because I'm an introvert and while I do enjoy socializing with friends I equally, if not more, enjoy time spent by myself not having to interact with people.
I'm single, never been in a relationship, and have a dog. However, she does not and will not replace people. I got her because I wanted a dog, not because I was lonely and wanted companionship. I haven't given up on finding a LTR/spouse, but I'm not exactly looking either, I'm quite satisfied with the status quo.
To consider a dog as a substitute for a person in my opinion disrespects both the dog and people. For one thing, as a person, one might understand that when one meets another person it might work out to be a STR.
For dogs, a STR may be a necessity during a boarding/training process or while waiting for adoption, but I do not believe they have a good understanding of temporary relationships, and probably do better in a LTR.
Dogs have unique qualities (and so do people).
Dogs do offer companionship, and affection, and loyalty, but in different ways than people do.
Some people are perfectly happy not having a LTR whether or not they have a dog, and that is perfectly OK.
I have to agree with some of what Lucille says. I have to say that there are plenty of people that prefer to stay single and childless and just have animals. If you find that lifestyle satisfying and it makes you happy then more power to you.
However, dogs can never be substitutes for romantic partners or children. Nor can children and romantic partners be substitutes when you want a dog! If that's what you're asking or looking to do then you will be disappointed.
Also happily single. Also have a dog. And a cat Have to agree with everyone else here - dogs are not people and do not replace those connections with people - they have their own special connections. My own circumstance has given me thought over this from time to time, mostly when I'm fed up what the dating seen has to offer (so like, always) And tho I'm not actively seeking a LTR at the moment, it's not completely ruled out in favour of the furry companions - but I am leaning towards that single, childless, pet-filled lifestyle! Haha.
I was a cat person, until I got divorced (16 years ago ) and woke up alone to some noise, thinking "if I had a dog, I wouldn't have to worry about noises in the middle of the night". Two weeks later, I had Duke. What a great dog he was! But like everyone else said, if you are getting one to replace an LTR, not fair to the dog. That being said, I do prefer spending quality time with my dogs rather than the dating scene.