More importantly, they provide a "point of reference". When working a print you can compare your wet work print to the reference prints on the wall to make sure that your eyes aren't deceiving you and you end up with a too dark or too light print. There should be one reference print of each style of image (portrait, high-key, low-key, straight landscape, street scene, etc.) on the wall near your development trays. They don't need to be the world's best photos, but they do need to have the representative tones you are seeking in your work.
Originally Posted by Worker 11811
Once you have your wet work print matching your reference print, then just dial in your drydown compensation for the final print.
A few of us did a print exchange recently which I'm impressed with the tonalities of several of the prints--tonalities which I'm wanting to mimick in some of my own work, so those prints will be going up on the wall in my new darkroom.
I've known of photographers to keep a binder with reference prints in, but that just seems to take away from the glance up and down ease of prints on the wall.