Shaving off some weight meant easier transport for the Ops, and less in shipping costs.
It did look better, and as you said, prevented things like drinks from being placed on top where they could be spilled all over the players.
Heat can escape using simple vents, or fan propelled out. You can push cool air in at the bottom of the cab, and pull it out or vent it out at the top.
Monitors generally dont mind the heat.. but computer components do... so its best to keep the bottom cool as possible.. and vibration free if you use a standard Hard Drive. (bunjee mount the drive or something)