There are several reasons my pictures are framed the way they are.
Most of them are framed in gold, silver, or black metal with single or double white mats.
The mat sizes are usually 16 X 20 or 22 X 28 inches with glass or Plexiglas and foam core backing of the same size.
This framing is usually readily accepted in art shows. I feel the painting is the subject, not the frame. These frames are not expensive and so my prices can be more affordable by more people. If one wanted to re-frame they could take it to a framer or could find one in any ready made shop because the sizes are accessible. I do have a few that I have done that way.