This is a multifaceted question on a subject I just want a little more clarification on. I've often heard that in many campaigns or battles that, in a general sense, that "this road junction/crossroad is a vital importance". I've also noticed that the names of a handful of battles in the American Revolution and American Civil War end with either "courthouse". My questions are:
I can re-clarify if my question might seem too vague.
Many of the courthouses were on the main road or near it and near the centre of town. This was at a time when the majority of people would have been walking, having the courthouse central to the people was usually therefore the case (this is not the case everywhere mind you.) The names of the battles usually come from the involvement of the courthouse somehow. Appomattox and Monmouth used these courthouses as staging points. These were usually estately places where the generals and commanders could rest and plan. Control of these places meant control of the governance of the area (or at least gave the implication of that.) Spotsylvania Courthouse does appear to have to do to its location at an important crossroad, however, so there do seem to be cases like what you're looking for.
Maneuverability is the main thing here. Look at the Battle of Great Bridge during the Revolution, there is one main road, and then swamp all around it. Sure, we saw troops utilizing guerilla like tactics and going through the swamp, but this was a difficult task and they got lost.
Keep in mind too that the military creeds of the day meant that such guerilla tactics were seen as counter to the ways of gentlemen's warfare. The British kept marching down that road, and were decimated, losing about 1/4 of their troops, while one American injured his thumb.
Hope his helped, let me know if you have any further questions.
Roads were absolutely essential for early modern armies. Just think of the supply situation for an army of 30,000 men. You need to feed them a pound and a half of bread every day for a bare minimum. That's forty tons of flour that needs hauled around by the army and baked into bread every single day. A week's supply requires 250 carts to move, and the horses pulling those carts need about twenty pounds of feed each every day, and the horses pulling the carts full of feed for the rest of the draft animals need feed as well. It's a massive logistical undertaking, an early modern military operation, and the only way to get the carts your army needs to survive moving is to put them on roads.
Same for artillery; you can't fight a battle with artillery, and hauling a gun that weights a couple tons over every little dip and bump in the ground, between trees, through bogs, and so on is going to eat you alive in terms of speed and sustainment. The slower your army goes, the more supplies it's going to need to go any distance. Like, imagine if your army marched everywhere deployed in its battle formation. A single company formed up in line is much slower than in column, having to constantly negotiate obstacles and stop to get lined up again. Early modern armies were not fast, even under the best of circumstances and in march column; trying to get anywhere offroad is a recipe for a logistical and operational disaster.
Furthermore, in many ancien regime armies, desertion was a consistent problem. The troops were usually the lowest of the low, with meagre pay and no particular loyalty to the king they fought for; debtors, criminals, drunks, Irish, serfs, prisoners of war, and they were kept in line with brutal physical punishments.
In the Prussian army, one punishment was for your company to line up on either side of you, and make you walk between the two lines while they beat you with sticks. You can't rush through because another soldier is marching backwards with his bayonet leveled at you. Your company sergeant doesn't carry a musket to shoot at the enemy; he carries a half-pike, so if anyone tries to run away, he can run them through. What they wanted was 'corpse obedience'; you could get shot and killed, but don't let that stop you from marching, loading, and firing in time with the rest of the company.
In this context, and with so much money going into the provision of supplies for the army over the years it takes to turn a lout into a trained musketeer, is it really wise to put these guys in a situation where they can easily desert? Just think of how much money you're losing per soldier if they desert without having fought a single battle; marching them through a forest could be financial ruinous for the warlord in question, doubly so if they're then so short of soldiers that they lose the next battle, which very often meant the total destruction of the army.
With this in mind, Early Modern armies often sought to control roads by building permanent fortresses astride them, especially at major crossroads. These fortresses served multiple purposes. Obviously, they were obstacles for any invading army, but they also had offensive power, since when no besieged, they served as depots were supplies from the area could be stored, and used to support an army operating along a road linked to the fortress. If an army was defeated, these fortresses served as shelters it could be evacuated to, lest it be destroyed by the pursuing enemy. Here, the enemy might be tied down until a relief force could be put together to cut them off and destroy their army.
Check out The Army of Flanders and the Spanish Road and The Military Revolution by Geoffrey Parker, as well as Wars in the Age of Louis XIV by Cathal J. Nolan, and The Art of Warfare in the Age of Marlborough and Marlborough as Military Commander by David Chandler for general surveys of Early Modern warfare.