If the screens are visible to all and no one is attempting to hide them then there is no harm in passing a quick peek. However as proper etiquettes would dictat

If the screens are visible to all and no one is attempting to hide them then there is no harm in passing a quick peek. However as proper etiquettes would dictate, it is not good manners to just stop and stare at someone's screens without letting them know or asking first. Reading newspapers over someone's shoulder is frowned upon and is considered bad manners. You can apply the same analogy here as well. And use common sense in such conditions. Not all matters are binary. In your case, you can purchase privacy overlay screens and apply them to your monitors if you don't feel comfortable sharing yours.