The players don't need any additional help from me for them to chase red herrings or draw erroneous conclusions. They can and often will do that on their own.
As well, faced with a low roll on the die and subsequent information from the DM, a player may believe that the information they were just given is false and discard it anyway. By telling them they get either the info they wanted or, on a failed roll, information that is interesting that they didn't want, it sidesteps this issue.
Sadly, it's difficult to avoid this metagame consideration without having the DM do all such rolls in secret, which takes away the fun of players getting to roll dice.
@DEFCON 1 , I hear ya; but my more usual take is that if the PCs don't go looking for info the chances are very high they won't find any, whether it be true, false, or irrelevant.
@Charlaquin , there's tons of potential advantages in giving deceptive info now and then:
--- distraction (the PCs end up
here while the real stuff's happening
there without interruption by pesky adventurers)
--- delay (whatever the PCs are doing take longer in the fiction, which is almost always an advantage to their foes)
--- danger (the false info can lead the PCs into a trap, an ambush, or even an entirely different adventure if they so decide)
The latter two also have potential to burn some PC resources; not as big a thing in 5e as in older versions, but still worth considering.