Hummel Clarification Please

[Oddball]

I can't wrap my mind around something, and I'm wondering if anyone else has the same thoughts on this:

The Hummel - It has the Indirect Fire capability, where "If a friendly Spotter is within 8 hexes of an enemy Soldier and has Line of Sight to it, this unit's (the Hummel) attack against that Soldier ignores LOS"
So basically, the Hummel can fire with Indirect Fire at a Soldier as long as a Spotter with the "Spotter" sub-type listed near it's type on the card, had LOS to the target at the appropriate distance. Simple enough.

What I'm having issues with is: Why just a Soldier unit (infantry or artillery) and not vehicles??? This makes no sense to me!

If I had to guess, I would venture that perhaps the designers decided that a lone Hummel's spotting support would be less so than say an Artillery squad's network; the latter having a more prevalent (read: larger) spotting presence on the battlefield; or just a fact that Soldiers move slower than vehicles, but I don't think this would be a great reason IMHO.

Anyone have a clue what's up with just Soldiers as "Target Worthy"?

Does anyone play it (the Hummel) capable of hitting vehicles?

Thanks!!!