It would be so helpful if there is a set of rechargeable batteries that change forms to tell you how “hungry” it is.
The thinner it is, the emptier the battery is. When it’s full, it’s just as straight as a normal battery.
Another merit is that when it’s thin, it’s much easier to take out from a packed battery room, especially if there are multiple betteries packed tight in line. Fat batteries don’t need to be changed anyway.