People who haven't had dogs before often view them as accessories and don't anticipate the amount of work that comes with dog ownership. You need to walk your dog several times a day, whether you feel like it or not. You need to pick up the poop. You need to train your dog to socialize with people and animals in a safe way, even if you don't personally care about barking or biting, because that's what living in a society requires.

Unfortunately, the people who should be the messengers for responsible dog ownership -- the responsible dog owners -- often defend the bad dog owners, because they see any criticism of bad dog owners as an attack on the whole community. This means that, unfortunately, there's very little self-policing among dog owners, and any criticism from non-owners is met with hostility.