"FRAME ONLY"

1). Technical / "Glass touching art" issues.
If you are framing something that is of significant value and requires glazing (glass, acrylic, etc..) you will need to utilize some form of "spacer" to keep the glass from touching the art.  Technically, art should never touch the glass because of "out gassing" from the art and other issues such as humidity & mildew that adversely effects the piece.

2). Less expensive.
This method of framing is usually less expensive because there are less parts involved.  Each "layer" of your frame job has a $ value attached to it.
For example...(from front to back)...
Frame / glass / top mat / mid mat / bottom mat / art / backboard / sealing paper / hangers & wire.

3). Simple.
Some people prefer the "simplistic approach" to framing. "letting the artwork stand out" etc....to each his own.

4). Frame matching.
There are 2 ways to best utilize "frame only's".
a). making the frame "blend" with the art or...
b). making the frame blend or match with some existing framing or wood tones that are near where your art will hang.
These are both important considerations that should be addressed at the design counter.

"Leopards" Hand-made from actual tree bark.

Fillet used on inside of  frame to add a deep red accent.

Small gold fillet used in conjunction with a deep colored mahogany frame for accent.