That's a question that will most likely create a controversy between dog lovers and people who love kids. I noticed there is quite a tension between the two. I used to have dogs when I was a teen and young adult and at that time I didn't want to have my kids. I just thought dogs were the right option for me.
A few years later, though, I found myself ready to have my family and have my children. I see many people who choose to have pets instead of children. Sometimes they are single and owning a pet is much easier than raising a human being. You can also leave your dogs for quite some time alone at home while you can't do it with children.
As far as making a conscious choice to care for a dog rather than an adopted child, I guess it is a personal decision and can't be generalized here. While I had dogs, I was also a dog groomer and a dog handler and I could see a trend where people would invest themselves heavily in their pet and treat him as their child, even more so because with a child you use logic, love and discipline and with dogs people sometimes forget about logic. I could see them feeding chocolate to their dog and not thinking how unhealthy it is for it (chocolate is a no no for dogs) because the dog begged for it.
Yes, while it seems controversial on some level to see people choosing pets rather than humans, we must not forget we never know what their personal motives and circumstances are.