There is a size difference between humans and domestic cats which we have got used to because we are the large ones in the relationship. It does not bother us.
But how do cats feel about this size difference? A study on dogs indicates that small dogs in general are more aggressive than big dogs. The reason: they feel vulnerable and fearful because of their diminutive size. That is a suggestion not a concrete fact by the way.
My point is that domestic cats might feel the same way in relation to their life in the human family home. It may be one reason why they can be a bit fractious or defensively aggressive sometimes.
We can only imagine ourselves how we would feel if we lived in a home in which the owner was about 20 times taller than us.
We can do certain things for our cat to overcome this emotional issue and you can read about those by clicking on the link above the image.