Listen to this and you may understand why they may need someone with good English on board. It is always unfortunate to hear anyone lost at an airport but at least when we are all using the same language then at least others are more situationally aware and can raise their guard accordingly.
When I listened to this recording I recall thinking the controller could have been more helpful with his instructions. The Air China crewmember was obviously struggling but the controllers use of non standard terms would not have any impact on someone whose English was already weak.
http://www.youtube.com/watch?v=iWDEIvjwaFU