Command block does not store conditional mode in NBT data

When trying to move a command block by control-middle-clicking (pick up with NBT), I find that it does not carry its conditional/unconditional mode with it and defaults back to unconditional. After researching I find that it isn't a NBT tag. Why isn't conditional mode a NBT tag? Thanks.

MCWiki link with NBT data: http://minecraft.gamepedia.com/Command_block#Block_entity