Yup. It's all about parsing FIX faster than the next dude.

Parsing FIX correctly faster than the next dude.

I've seen some fast FIX parsers. I've seen few that actually produce correct results :)

No it's about providing market liquidity in order to optimise the efficiency of production. /sarcasm

In some asset classes (e.g. equities) the exchanges and dealers have built their own proprietary protocols to reduce the excess bytes.