Beginner's question: opinion on cropping

Not in any of the competitions I take part in. All too often the external judge gives his reason for marking a photograph down as because the photographer failed to crop his photograph to maximise its impact or has failed to clone out unnecessary artefacts.

Some photographers treat their original photographs as sources of elements to be reassembled, taking bits from maybe half a dozen different photographs to create a photographic work of art that bears no relation to any of the originals.