The purpose is simple - it's to create meaningful photographs.(posted 8645 days ago)Some of us find meaning in the real world, some don't. And it's not random, it's the world around us. Some of my "street" shots are carefully constructed in advance by picking backgrounds where I hope something will happen and then photographing as people happen into the scene. Others just happen because the opportunity shows up.
Regarding tilt- it's just another compositional and emotional construct in the photo. If all photos conform to some template - strictly square to the edges, 8x10 form factor, "rule of thirds", no blur, etc., the world becomes boring and can be photographed by computers.