Why did military in the civil war era just use muskets?

The issue of musket and bow usage in modern times appears quite often here. I don't want to hinder further discussion in any way, but you may find useful information in the following threads:

This one, that discusses Franklin's opinion on bows and pikes.

This one, that explains popularity of musket in colonial times.

This and this thread about a similar topic, just focusing on a period half a century earlier.

This reply from /u/Valkine that explains the ballistics and other issues related to early firearms.

As we're speaking about the American Civil War, it is necessary to remember that the most popular weapon used in this conflict was Springfield musket model 1861, a rifled firearm using Minie bullets that gave it both good rate of fire for its era (that was and issue of relatively low importance in case of volley shooting) and substantial accuracy. Additionally, typical load cartridge with that weapon was ~510 grain bullet and ~60 grain load, usually resulting in the muzzle velocity close to 1500 J, what is an order of magnitude higher than energy of arrow shot from even rather powerful bows (usually in the ballpark of 90-110 J). And as bullets and arrows are inert projectiles, that energy would only decrease due to drag and gravity. This means, that archers would start to suffer losses long before closing in to actually do some damage. And also remember that Civil War saw a substantial use of rifled artillery, capable of inflicting serious damage from over a kilometer away, making an idea of returning to archery even more obsolete. And if this would not persuade people from still swearing by archery, then the introduction of rapid-firing Gatling's gun quickly followed by Nordenfeldt's designs would easily show them the error of their ways, so to speak.

Now, the one issue that is often missing from comparisons of weapon effectiveness is the economy. Because it doesn't really matter how 'good' a weapon is (whatever technical criteria we will take) if such weapon cannot be easily adapted on a scale suiting the fighting forces or if the cost of such adaptation (in money, time or effort) plays an important role in such adaptation, possibly eclipsing the perceived advantages. Now, how does this relate to the issue of musket vs. bow? The answer lies not in the weapons themselves, but rather their ammunition. Assumption that bows were more accurate than early firearms or that they were accurate at all is true only when archer has a high-quality arrows, that were properly selected, constructed and stored. Such process takes time and a lot of effort. This was not the issue in the heyday of archery, when the number of archers were relatively small and the actual battles were quite rare. In 19th century however, armed forces numbered hundred of thousands, and the total number of military personnel involved Civil War (on both sides) was over 3 millions. Use of archery on any reasonable scale meant making hundred of thousands if not millions of arrows, each one carefully made from a perfectly straight wooden rod that had to be harvested and seasoned earlier. This seems ridiculous even if there was a developed fletching infrastructure that, as much as bowmaking, actually never existed in Americas to any considerable extent. Just to compare, blackpowder could have been easily made on industrial scale in powder mills and use of more or less standardised steel molds for bullet casting allowed for making hundreds of bullets in a day by a single person in a camp, no special equipment necessary. So, in terms of economy, in the mid-19th century, bow was heavily inferior to a musket.