I spilt a glass of water on an old Lenovo laptop I had (while it was running), the keyboard had a tray under it which drained outside of the laptop. [0] But if i had damaged it, every single part was removable, orderable and replaceable.
Spill trays, albeit without the gutter, used to be a common feature, but they were a casualty of the thinness wars. A super-thin spill try can't hold much liquid, so what's the point? I like this solution from Lenovo.
Being able to pull a laptop's battery as soon as liquid was spilled on it was another great feature for survivability. Water doesn't directly damage electronics in and of itself. The damage is usually done by the short-circuits liquids facilitate. Disconnecting the battery before the liquid spreads through the device can prevent a lot of damage. I suppose the thinness wars probably killed this feature too.
The mac keyboards have a nearly hermetic seal on the backside, the backlight is backed with plastic and rubber and soft-glued to the backside of the keyboard tray.
If you do spill on a mac, flip it upside down asap and power it off asap. Then remove the back panel and disconnect the battery. The keyboard might be lost, but the rest of the computer is usually fine.
[0] http://blog.lenovo.com/en/blog/avoiding-water-on-the-brain