The reason is that the American soldiers fighting in these wars were a part of conscription, and not (only) those that enlisted in the Army, knowing all the risks and receiving a good payment. It could have been anyone and people often personally knew soldiers who did not want to go, but were forced, and maybe even died.
This was especially bad, as many, many American soldiers died in these wars. Often these were not professional soldiers, but men forcefully torn out from their families.
