This is what my frame looked like in a Lodon gallery (Photfusion) where space was tight (part of a group show), This is why it's important - as the previous poster says, it separates the images from the wall, but I'd add also from each other.
But there are many other alternatives, it's personal, I also use the wood finish as it compliments my subject matter, and I prefer wood with warm-toned prints.
Many people use the satin finish aluminium frames they are more robust than wood, and come in various colours, but the natural anodised seems to work best with a wide variety of types of image. Many Galleries use these as stock frames.
Ian