yeah, it is tempting to stray towards a very pessimistic view of what Taleworlds are doing with M&B... Are they just cashing the cheques now, or are they half-way serious about completing their games?
Horses remain, as they were in the very first versions, nothing more than a speed bonus/platform for archers. There is no reason for this other than the developers skimping where they can get away with it. Mods have been created - including by me - where some simple code lines allow you to have 'hero' horses that will upgrade, and potentially be killed. You can add equipment and training upgrades so that your hero horse gets a mail coif, double girth strap, bigger muscles, whatever. There's a fair bit of code involved by this point, but its not hard, just repetitions of the same code block with a few variations.
Still, the basic limits of the horse are killers: It can only do blunt damage with momentum, so modding a 'horse bite' skill - although possible - becomes extremely time-consuming.
It can never think for itself, as a good warhorse should and a real animal would.
It moves like a ship: forward, backwards and in arcs, but never sideways, like horses actually can.
like AI troops, it knows no fear....