Commercial breeders share the majority blame for fully knowing what they're doing is wrong, followed to a lesser degree by the ignorant masses that fall in love with cute animals at pet store windows. Unfortunately, my mom and sister are in that group.
My sister became infatuated with owning a pitbull and babysat one for several weeks with the intent to eventually own it. She was almost never home to walk him, clean him, or train him properly; pretty soon, he was nipping at us and peeing and shitting all over the place in a penned area. This was the start of a disaster and I forced her to give him back.
Several years later, my mom bought a small dog (Japanese Chin) without consulting any of us and without any real knowledge of caring for an animal. I didn't want the thing initially, but grew attached and learned about what it can/can't eat, walking it, etc. My mom threatened so many times to get rid of it because his coat blows out a couple of times per year. Initially, I said "fine" out of frustration, but over time I said "no, he's mine now." I moved out from home and came back a month later to take him with me, knowing my mom wasn't going to pay for vet visits, walk him to the park, etc. He just turned eight last month and my GF and I love him so much.
Before I moved out, my sister again got another pitbull pup. She started nipping after our Chin, and again I noticed the same pattern of ignorance and lack of training, although it was no longer living in filth. I forced her to get rid of it, knowing fully well we would come home one day and find our smaller dog dead or injured. Large/powerful dog breeds should never be owned by irresponsible, inexperienced or absentee novices.
Again, sometime before moving out, my sister got an easier dog breed: a common Shih Tzu. Not its fault, but was it was an annoying little thing (my Chin hated it), and always looked/smelled dirty. Eventually she grew bored of it and gave it to her fiancee's parent to care for. He's still around, but it's a classic example of a decent dog that nearly ended up at a kill shelter because of a bad owner.
So what's the solution for a person who isn't sure if they have what it takes to fully commit to caring for an animal? Temp foster an animal to see if it's for you. Adopt an older pet that's already trained and low energy/easier to handle. Get a low maintenance caged pet (fish, hamster, lizard, etc).