i think that is an overly simplistic axiom: the utilities must cover a fixed asset base (poles and wires and transformers), pretty much regardless of how much or whether a household consumes from the grid.

the less the utility recoups via billing for energy usage, the bigger the deficit to cover their fixed network costs.

they are frequently interested in having you consume energy, to help defray those costs, especially where the marginal cost of the energy is very low.

the more users who disconnect, the more the fixed costs must be recouped from a shrinking customer base, triggering more incentive to leave the network. this is called the death spiral.

In addition, things like balcony solar don't save them cost: it introduces complexity because they need to safely manage that load, they need to be able to predict and measure it; in my experience working with utilities and network operators for many years, they flat out don't want these distributed generation sources unless they have a lot of say in how they are added to the grid, and how users can be charged for the privilege of generating their own power. that is often a very significant barrier to regulatory change.