I put this on just prior to doing an FarRide (1642km) through dry and wet conditions and several roadworks, and it's worked a treat.
But, is it needed, costs all of less then $2.
Yes, is my answer, as it stops all those little pieces of blue metal etc from the road, which are a pain to clean off.
(As a side note, I use old tooth brushes with double sided tape on my metal bandsaw wheels for a similar reason.)
Buy a synthetic painting brush, remove handle, squash metal ferrel in vice/piers, bend a 90 degree on the handle end, cable tie, your done, so have a beer and write it on your farkle list.