It honestly depends on your hair type. If its oily, you probably should wash it everyday. Normal to dry hair types, should wash every other day. It just strips your hair of its natural oils and nutrients. It drys it out. I wash one day, then just condition the next day. (so I'm not washing it, but it looks a bit fresher and feels fresher) or I just brush it and fix it the no wash day.
Washing your hair everyday is not bad even though it is important that you use the right shampoos when washing. Therefore, it is important that you stay away from harsh formulas that destroy the natural oils in your hair.