Curious: Why are battles resolved instantly?

To dream on further and add to what Janosch suggests about tactical options, one thing I would love to see in some far removed hypothetical update was the possibility of setting formations for your armies. 

Imagine a grid resembling the battle field: You could place speartroops in the front if you expect to be met with cavalry, have units of cavalry placed on the far sides of the field, ordered to use flanking manouvres ect. All this would ofcourse be set before sending the army off to battle. This would not only allow tactical minds to battle out in a whole new way, testing wits with opponents on the best army formations, but also create an incitement for using mixed troop armies.

As it is now, the only sound strategy is to focus on one troop type per city and churn out as many as possible. An army comprising only archers is hardly realistic, even though I fully accept that realism is not the key in a game like this :)

I know this is far fetched and not likely to ever be implemented, but just think of the possibilities!