I also have them on all my cues. They look cool, some make it easier to remove the cue from the case (especially a JB case) and do protect the pin and collar. Only draw back is occasionally, your opponent has to be a bit more patient while you get ready for your match.
I have quite a few from Lonnie Wilbur, several from Steve Kornelle and one amazing set from Alton. I usually include them when I sell a cue; but somehow I have about a dozen or so orphan sets.
Actually Steve is making two sets for me now for 2 cues I recently got from Dean.
I guess in todays world its just another toy in the billiard host of "stuff".
When I first started playing about 45 + years ago, if you didn't use a house cue ( I used to hide my favorite under the rail of a table at the Golden cue) and had a 2 piece you were lucky.
Most players had a cue with two shafts, one for straight pool and one for Billiards. No break cue, no jump cue, no bridge head, anyway we all have our memories.
Today, I have all the junk and its a very pleasant past time.
Best regards
Dave