Stupid question about tire wear

I'm having issues with tire wear. I am only at -4.5* of camber in the rear, however, only the sidewall and very little tread see wear. 

Question: Is this due to needing more air pressure in the tire or because of the weight of my car? 

I'm trying to get a picture of the wear uploaded now.

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Its because your driving lol, tire will still lose life.

Make sure the psi its to what the tires require.
Running camber plus weight and mileage adds to the tire wear when the thread gets low flip the rear tires.

Check your toe. Most of the time, it's the toe that kills tires, not camber. Your tires will love you once it's fixed =).