are Skin/Protective covers/Palm Rest/Keyboard guards and Protective Cases not advisable to use?

I've been an apple user for more than a decade now and i have always use protection to keep all my apple devices safe from any type of external damages (like scratches). However, I read that you do not advise the use of keyboard/palm guards because it will defeat the purpose of the laptop design. By this, does this mean that we should not use any type of skin guards (screen, keyboard, palm and track pads) and any type of protective cases (external)? If so, how can we keep our laptop safe and prevent scratches? Please advise.