Some don't understand their responsibilities when it comes to such work, some are badly advised by builders or salespeople who want to avoid the bureaucracy, some other will feel that they are entitled to do what they want with their own property and don't consider the consequences, etc..
It's very likely that anyone else considering purchasing this property will uncover the same issue, so it's certainly not the end. Which particular chapter it is in the story all depends on how the owners respond.