Why? What makes you think people want to pvp in their space? They don’t. They want to fight people in the other guy’s space. Just like you don’t leave your door unlocked and wide open so people can walk into your home and kick your butt and take your stuff.
People, even in EVE, want their homes to be secure. So they respond with enough force to try to make people not want to come attack them. It’s not exactly rocket science.