Im sure this has been said lots of times in the past, but cavalry (especially under AI control) will never lower their spears and/or lances in a charge. However, giving cavalry a 30 "charge distance" actually makes them charge okay (at least most of the time).
However, Darth has said in a lot of threads that "charge_dist", if well configured, makes the AI handle units better. So, would restoring the 30 "charge_dist" make the AI crappier or not:hmmm:?