First, general plumbing means that you’re able to safely list a home for sale or rent without concern for regulations. It’s liveable, it’s safe, it’s not going to cause anyone any harm – it’s compliant.
Second, it ensures that your home is both a great place to live and an easy place to advertise. Nobody wants to move into a place where they require additional work – it’s an easy way to put up a strong value on your home and justify it.