Why increase battle difficulty level?

[divad]

I'd like to know if I am mistaken: I believed that battle difficulty level above normal simply added stat bonuses to your foes. And not making the battle IA "smarter".

If I am right, I am not interested in using it, for example if I play dawrf I don't want basic goblins to be better than basic dwarves.
When I want a harder challenge (and I usually do), I simply increase the campaign level difficulty. Using the same example as above, I will fight much more goblins than in normal level, but they'll still be goblins, and not improbable monsters disguised as goblins...

Simply messing with the balance between units, seems to me a very awkward and unimaginative way of increasing difficulty.

[Alhaioth]

Higher battle difficulty gives AI flat combat bonuses, higher campaign difficulty gives AI flat campaign bonuses. I don't know exactly how big they are.

It's hard to find a game which doesn't do this, really.