I use one for tracing applique or embroidery shapes onto fabric. You could also use one for tracing quilting designs onto your quilt top. I had a make-shift light box (a piece of plexiglass laid on top of two plastic shoeboxes with a folding Ott light underneath) but I recently bought a CutterPillar, which comes with a self-healing cutting mat. I love that it's completely portable, can be used without being plugged in, and the light is evenly distributed. I got a good deal on it on the last day of the Houston show. I also got the glass overlay.
https://www.cutterpillar.com/glow-premium