-
Without it though you're exposing the pedal to the bolt heads of the adapter plate which is far more likely to damage stuff. Look at your top pic - looks like it's already eaten away some of the bolt head.
They also keep the lube where it should be and it would stop stones or anything getting in the gaps where the bolts are if, heaven forbid, you had to walk somewhere dirty.
Get some. Make Jesus happy.
First I've heard of such a thing. I think I'd rather the adapter plate wore away a bit vs the pedal though?