I guess they promoted this in average per person. Everyone is different, and everyone feels in need of a shower at different points of the day, or the week.
But what actually happens with showering every day, is that the human skin starts to get too much dry, and natural oils, which also work as defense against bacteria and diseases, can't do it's job. One way to solve this while still showering each day is using body cream.
In my case, my skin is too much oily, I shower almost every day to keep the natural oils in balance, otherwise blackheads start attacking haha