Fundamentally it is getting priced into services provided to residents as a whole. But you're also forgetting water is generally not provided by a business: Local government is not a profit enterprise, and generally has a lot of pressure to reduce (or limit the rise of, anyways) the bill.

I can tell you factually a lot of work goes into measuring leakage, narrowing down what part of the water system it is coming from (most active components are metered in some way, and you can use math to determine where all of the water is not making it through a segment), and correcting those issues where it is cost-effective to do so.

For profit water companies are common. Municipalities do not have the capital to replace infrastructure, so private companies like American Water buy the pipes and plants, make the minimum fixes, and jack up rates to pay back investors.