Not sure what you mean exactly. In the jurisdictions I have experience the utility is legally obligated to provide service to any residence within the territory. That resident can then decide to use 100% solar with batteries and pay us nothing, or use solar during the day and rely on the grid at night, or in our case we had net metering so resident were able to treat the utility as a free battery, producing excess kWh during the day and drawing it back at night, paying only the difference in total draw (or receiving a credit even).

I have not worked in water/sewage, but the characteristics are quite different compared to electricity--electricity cannot be stored, it needs to be sent directly from the power plant to the consumer at the exact moment it is consumed, but on the other hand electricity can be produced more or less on demand with the quantity limited only by your willingness to pay. Water is finite, and is simply being managed by the utility rather than created on demand. Someone collecting rainwater is still impacting the local water system and depending on the environment this still needs to be managed by someone.