"Don't shop, adopt"

I was looking at a post about someone wanting to get a puppy. I am confused about why so many women kept telling the OP to adopt a dog from a shelter instead of getting the breed she wants.

I'm not going to compare a human to a dog but this is the only way I can explain it. If someone told you to adopt a dog from a shelter, isn't it like someone telling a woman to not have her own baby and to just adopt a baby/older children from foster care or an orphanage?

*I said I know that they are two completely different things but I didn't know how else to word it.

*For the millionth time- If you READ the post, I said I KNOW that the comparison I made is not comparable. I ALSO said that I didn't know how else to put it.