I've always found that odd in football, but it seems to be a worldwide tactic for keepers to kick it long. So I'm thinking there must be a reason for it.
Is it just not worth the risk to be under pressure if they press you in a short pass from the keeper? If they do press on the keeper is it that you're better off playing the numbers advantage down the field so knocking it long is more sensible than playing it short and being under pressure?
It'd be interesting to ask a coach that actually, because I have always wondered.