They were well aware that not all nobles were like those forlorn ones. In fact, most nobles in existence today were from capable noble families, and they themselves had profound insights into the history of their own families. As such, they would not casually choose their heirs, because they must select individuals who clearly possessed such capabilities, and would not allow useless individuals, who had no abilities besides flaunting their noble status, to inherit. If such people were to take charge, it could very well lead to the downfall of the family. What's more, if it were merely their own descendants behaving this way, they would rather let the family perish due to the lack of a suitable heir rather than let it destroy the family's good name.