I don’t paint the sides of canvases.
It indicates that the painting is finished. I don’t consider my work finished. There is always something that can be improved or changed.
It can prettify the work. I’m not interested in pretty (unless it’s a device to lead you to something else). Beauty and pretty are not the same thing.
It’s a painting. I’m not interested in trying to make the painting into something it is not. It feels like it is trying too hard. That’s not to say that paintings are not other things. It will become what it will become.