Why does the "fdisk -l" command complain about "Disk /dev/mdN doesn't contain a valid partition table" for software RAID devices?

Issue

• Why does the "fdisk -l" command complains about "Disk /dev/mdN doesn't contain a valid partition table" for software RAID devices?

  [root@HOSTNAME ~]# fdisk -l
  
  Disk /dev/sda: 160.0 GB, 160041885696 bytes
  255 heads, 63 sectors/track, 19457 cylinders
  Units = cylinders of 16065 * 512 = 8225280 bytes
  
     Device Boot      Start         End      Blocks   Id  System
  /dev/sda1   *           1          13      104391   fd  Linux raid autodetect
  /dev/sda2              14       19457   156183930   fd  Linux raid autodetect
  
  Disk /dev/sdb: 160.0 GB, 160041885696 bytes
  255 heads, 63 sectors/track, 19457 cylinders
  Units = cylinders of 16065 * 512 = 8225280 bytes
  
     Device Boot      Start         End      Blocks   Id  System
  /dev/sdb1   *           1          13      104391   fd  Linux raid autodetect
  /dev/sdb2              14       19457   156183930   fd  Linux raid autodetect
  
  Disk /dev/md1: 159.9 GB, 159932219392 bytes
  2 heads, 4 sectors/track, 39045952 cylinders
  Units = cylinders of 8 * 512 = 4096 bytes
  
  Disk /dev/md1 doesn't contain a valid partition table
  
  Disk /dev/md0: 106 MB, 106823680 bytes
  2 heads, 4 sectors/track, 26080 cylinders
  Units = cylinders of 8 * 512 = 4096 bytes
  
  Disk /dev/md0 doesn't contain a valid partition table