A common sit-com site gag is the butterfingers magician or talent show goof who fumbles the deck and reveals that all the cards are strung together with string or fishing line or something.
But if done properly, what kind of sleight of hand magic does such a deck allow one to perform?
I don’t honestly know of any, although I know a little magic and have a trick deck.
The only thing I can think of is that is allows the magician to send the pack of cards in an arc, from hand to hand, without dropping any, and having them all come together in a neat stack. Obviously it couldn’t be used for any sort of trick in which you could see the individual cards clearly and completely.
I suspect it was chosen as a “typical” trick deck because its shortcomings could be revealed instantly and quickly, and grasped immediately by the audience – it’s a Trick Deck for a Quick Laugh.
real trick decks use much more subtle methods for working their tricks, be they subtle markings, subtle variation in dimensions, or unseen additions.
Or possibly just let him make that perfect “spread” of the cards on the tabletop, followed by that little deck flip. Not that those are too difficult to learn with a regular deck.
It’s called an “electric deck.” You can buy one from a magic supply house or eBay. As you surmised, it’s simply a visual effect and doesn’t do anything else.
But if done properly, what kind of sleight of hand magic does such a deck allow one to perform?
None. It’s simply used for “card juggling” and then only by kids. No real performer would ever use such a deck except for laughs.
On the other hand, I’ve seen Ricky Jay use a waterfall to reveal a card. They all fall perfectly into his had except one card that falls on the table - your card. Obviously, that couldn’t be done with cards all strung together and Jay is a master card manipulator and has no need of such cheesy tricks.