Parents who have kids share their location with them during transit times to and from school or a friend's home will find the battery life feature useful. A parent would be more at ease if a child shares their location data showing that their battery is at 5 percent, which would give them a heads up if their don't receive responses in a timely fashion later on. They would then know that the battery simply died, rather than something nefarious happening.
This feature will be rolling out to all users and if you don’t have it yet on your maps app, it should be landing soon. It's not clear if you can turn the battery life indicator off if you don’t want to share that information.