I've been a crosstitcher and designer for 25 years, i do think it seems to have fallen out of favour in recent years as a hobby. I would always recommend you wash any embroidery project once it's finished, unless you have only handled it wearing cotton gloves, as the oils from your hands can cause brown staining over time. If you are not sure of the quality or origin of the thread then it's a good idea to spot test a small area for colour fastness. I normally hand wash with Dreft or similar mild hand wash liquid as rowan describes. Never wring or spin your work as you can ruin the stitching, you should lay it out flat on a clean white towel then roll it up and this should soak up the excess water. Lay it out flat on a fresh dry towel and pull gently back into shape and leave till almost dry. While still vaguely damp place face down on a clean folded towel to protect the stitches from getting squashed and press with a hot iron. Try to handle the work as little as possible once it's clean or wear cotton gloves.