The /setblock command will reuse data from the block it replaces if the old block is the same as the new one. For example, if you use the command /setblock x y z sign[rotation=5] when at x y z is a sign with with text on it that doesn't have a rotation of 5, a sign will be placed with a rotation of 5 (expected) but it will keep the text of the previous sign (not expected).