One reason is that overall power consumption needs, timing and priority are going to vary a lot household to household. For one household a power outage might

One reason is that overall power consumption needs, timing and priority are going to vary a lot household to household. For one household a power outage might be no problem, for another which depends on life support equipment, a power outage might be life threatening. If you have centralized batteries, then the decisions about (a) how big they are (b) who they cut off if the battery is running out and (c) how the batteries impact the pricing of power are all made at the community level, which has value as a way to optimize the way an entire community draws from the power grid, but it lacks precision in how it helps individual households. If you have localized batteries then people can choose (a) if they need batteries at all, (b) how many batteries they need and (c) how they want to use the batteries to offset their grid usage (some people might want to rely on batteries mainly for emergencies, others to aggressively charge and discharge based on different price levels throughout the day). It might be less efficient in aggregate but it is much more accurate in terms of delivering the benefits to the people that need them.