I mean, you can make your soldiers hold a formation if you want. I think some peple need to understand that while BN's battles are massive compared to other games of its kind, historically, those hour long battles with clashing formations where on a totally different scale.
The average large scale battle will have your side command between 200-300 infantry, that is simply not enough for the kind of warfare you are describing, since any formation would easily become surrounded.
What would make battles last longer, would be uping the priority soldiers give to blocking (IRL, most soldiers, even on the frontlines, played it pretty safe), but that would make combat significantly less fun imo.
Also, I find the time a battle lasts really depends on who you are facing, I've had armies constantly try to skirmish and then backing off, and others than charge me and flank me right away.