Officers in the Confederate Army had to supply their own uniforms which were usually frock coats. However, late in the war it was authorized for officers to buy jackets from the depots if there was a surplus. This was due to short supply of material in the South since all that was available was being obtained by the CS government. Many line officers likely obtained uniforms in this way. It made them less of a target. If you look at some of the high end memorabilia dealers web pages you will see original frock coats for all grades of officers from lieutenants to Generals offered for sale. Also the material for these frock coats was usually a fine grade of wool and not the horse blanket thick wool some modern reproductions are made from. A well put together frock coat made of proper material is not that uncomfortable except in the most extreme hot weather. Remember those folks back then were not used to AC. Many also wore vests on those hot July days to keep from catching a chill.