Why doesn't the app indicate 12V battery level?

Since I've moved to my new residence, I've been left with a dead vehicle twice in one week, despite having driven the car the day before. I have a battery maintainer, but no way to plug it in. I am frequently faced with an inoperable vehicle due to "battery level too low," requiring a boost.

Of course the stupid reply is always: "replace the battery" or "fix the parasitic drain." But both those avenues have been exhaustively pursued, hence the battery maintainer (and the boost-pack).

This is a serious flaw with my Prius Prime. The battery can run down to a level which disables the car, sometimes within a few hours. A way to check the battery level from the app would be a helpful start.