There are a few people who like to gaslight and say its not an issue and that apple designed the laptops perfectly and all that, but of course we all know that the display can touch the keys and thus the keys can damage the display. Neither assembly is perfectly rigid and laptops are subject to all kinds of dynamic situations, even in a backpack or briefcase.
Apple shows us the best way to prevent the wear that results is to prevent the two from touching, but of course they can apply those paper protectors in a clean factory setting. In your case, where do you put the protector when you are not using the laptop? do you clean your hands before you use it? how crazy do you want to get with it? There are some on this forum who will say they only use their laptops in what amounts to cleanroom conditions, whether that is mentally healthy I cannot say
The difficulty is making sure that whatever goes between the keyboard and the display stays *perfectly* clean on the display side, or else it immediately begins to work against you by pressing whatever debris it's loaded with into the display. the thicker the protector, the worse this is. I think I have the best of both worlds with a screen protector from viascreens...I don't worry about it and I believe they shipped me a spare if I ever decided I wanted to take this one off.