Apple has released a new device that is meant to connect to your local wifi network and plug a network device on it. This device also has an audio output either with a 3.5mm Jack of an optical output (from the same Jack). Apparently the format to transmit audio in the Airport Express is Apple's Lossless codec.
http://www.macworld.com/weblogs/editors/
That may explain why they favoured speed (compressing/decompressing) instead of compression.