> Wouldn't the attackers just "accidentally" spill coffee on your laptop?
The difference is deniability, you can always see that someone killed your laptop with coffee or smashed it with a hammer, with this you wouldn't know until you can examine the circuits.
You're in a coffee shop. Wouldn't the attackers just "accidentally" spill coffee on your laptop? Some laptops cope well with water from the top (over the keyboard) but not in the air vents.