Power symbols are still a bit of a kludge in KiCad.
The underlying problem is that KiCad derives a global label from the pin name of the power symbol, and that is not editable in Eeschema itself. The text of the pin name is also hidden, and the text you see of the power symbol is the “value” field, and this has been made read-only. This is a kludge on a kludge.
As a result, a long time ago a bunch of these power symbols ended up in the symbol libraries, and usually you find something there that is “mostly adequate” for your project and use it without giving it much thought.
The current situation is “workable”, and most people who have used KiCad for a longer time have probably gotten used to it, and I’m guessing that it therefore it has a low priority.
A real solution is to make the text itself editable… I think this is already planned for the next KiCad version.