The intent is that units aren't going to waste ammo firing on hexes that they don't know are occupied by enemy units (yeah, you see them but you're units on the map don't). It's how the spotting mechanic, which is the fulcrum of the system, comes into play. It (the spotting rule) is all very logical.
There are many who do not like the lack of area fire (or spotting). There's an article in LoF 15 that I co-wrote with my dad (who despises spotting) that provides an optional solution/bridge to get spotting-despisers and area-firers into the system. It allows area fire with a penalty. Fire away.