I think it's a combination of ignorance/mental protection. It's mentally taxing and depressing to realize that so many people are being oppressed by the system due to no fault of their own. It's the reason there's such vehement backlash against teaching any amount of critical theory in the US, because it basically amounts to realizing "everything you ever knew was a lie, and life is profoundly unfair". It's deeply unsettling to think that someone is suffering because of random chance and the systems we've built, so instead you reject it and comfort yourself by victim blaming instead, because then you don't have to worry about falling into that same hole.