There's a couple of different aspects to this, construction being one. They were produced by wrapping a tread compound round a completed carcass and overlapped to "join" that component, which would allow torque to pull the leading edge up and start to unwrap the tire if braking or traction were applied in the "wrong" direction. That's obviously the structural element in addition to which production may have moved to complete bands of tread compound currently used with no join.
We had an explore recently in this area
http://www.sohc.co.uk/index.php/topic,23441.0.html as to the tread pattern, orientation etc.
Since which time I asked a tire engineer the same question, the answer to which was, the front tire particularly has no real prospects of aquaplaning. It presents to the road surface in a "canoe" shape and as such doesn't build water between the two as a flat tire would. The two sides of the centre line can be considered as separate parts as you lean it over with the opposing side simply not in contact.
The pattern is solely designed to give the correct feel to the rider as they lean it over and approach the tire slipping. This is obviously a compromise in terms of ambient temperature and just how much force the rider puts through it at extreme loading. Hence high speed/load tire for high temperature will usually have minimal cuts and harder compound to support its intended use, as a pure road tire for general temps will ordinarily be away from that to give the same feeling at much lower loading.
