From a dealer's perspective, I would think they are probably a necessity. Tags add a certain panache, a 2-cent provenance that not only frees up the dealer's time (as he or she doesn't have to answer basic attribution-related questions that are addressed by the tags), but IMO provide a certain degree of psychological comfort level for the prospective buyer.
That being said, as you know, you buy the club, not the tag...
Now... I
do know one dealer (of a certain TV show fame) who goes a step further and uses antiqued cards with yellowed twine. Every item tag looks as old the as item to which it is attached!
