I think you might be surprised at the answer.

Let's take Gettysburg. Most of the lands where the battle was fought was pasture land with active grazing. If you were standing on some of the hills around Gettysburg in 2020 and looked through the woods, you would see dense underbrush and very restricted visibility. But, in 1863, those areas had no underbrush as animals ate the underbrush clean.

That is a very common thing in an agricultural area and era. The best lands to fight a battle were also the most maintained and managed lands available to the local settlers. Even areas that had crops planted were notable only when they impacted battles. Antietam was notable for the height of the corn in the north end of the battle. Completely obscured the visibility of the attacking federal troops. But, had that battle been fought a month before, the corn would have been much shorter and 2 months before, would not have been even remarked upon. The wheatfield is as notable at Gettysburg for the shear confusion of the battle as anything else.

Defenders looked for higher terrain with clear sightlines wherever possible. Attackers looked for easy terrain to cross and get into the defensive positions as soon as possible. Clearings were sought after, especially if there were things like a fence on one side to use as cover. Well maintained roads and water were also favorable to army movements.

All of the factors tend to funnel battle locations to well settled, agricultural areas along transportation lines.

In short, land management practices using livestock grazing combined with seasonal planting cycles meant that those areas would have a more manicured look than one would expect. And, those factors factored into the site selection for battles.