[andrewcooke]

if you read the article, it's because the faster alternatives use multiple streams and/or use compression. it's got nothing to do with encryption. and you can get scp to compress your data first (-C).

[diginux]

Compression also slows it down: http://www.spikelab.org/transfer-largedata-scp-tarssh-tarnc-...

This has been my experience in practice, too.