You have good reason to be confused about what "threats" these products are actually targeted at protecting against: not one commercial that I've seen for these items actually provides clear, unambiguous identification of the exact threat that is supposed to be in play here. Every commercial that I've come across just demonstrates a bad guy carrying around some (unseen) device in a bag or something capturing animated waves of some kind emanating from an unsuspecting person's wallet or purse. Naturally, this would suggest that the shielding is meant to protect against attacks involving contactless cards. But the commercials also take care to not actually say that anywhere. And the way the announcer talks and how the "scenarios" play out conveys an impression that all payment cards are vulnerable to having payment info from them silently pilfered by a mysterious attacker.
Not being specific about the threat, of course, makes sense from a business standpoint: most people still don't have credit and debit cards that use contactless payment technology. (Cards like transit system cards are probably another story.) Meaning if you come right out and say that your protection only matters if you have any newer, contactless payment cards you are greatly limiting your market. So, even though that would be the only honest and responsible thing to say, there's an incentive for companies that are willing to use unscrupulous, fear-mongering tactics to leave an impression that everyone is vulnerable to attacks like these. When that's certainly not remotely true.
And that brings us to the question of whether even if you have payment cards that will do contactless transactions these products provide any security benefits to you. About that I'll note two things. First, smartcards with contactless EMV payment abilities, like other EMV smartcards, are specifically designed not to be cloneable even where an attacker can steal information from the contactless signal during a transaction. Or even from signals collected from many transactions. That's the inherent benefit from using a payment type that does dynamic authentication, rather than static authentication (as traditional magnetic stripe cards do).
Second, the name "contactless" is really sort of a misnomer in most cases. Often cards simply will not work to authorize a payment unless they are taken out of a wallet, purse, or other storage place they are in and physically tapped directly against the reader. Other cards (like my transit card, for instance) will work through the material of a wallet but not through the additional covering of, say, a winter jacket. The depictions in the ads of the bad guys' concealed gear being able to capture info from a card buried deep within a bag or inside coat pocket is ... unlikely.
Now, in 2013 some researchers in the UK were able to pick up some card data as far away as about 45 centimeters / 18 inches, well beyond the 2 centimeters or so the cards should ideally be readable at. However, the exact circumstances of how those observations occurred are a little vague, and it appears that the would probably not succeeded in trying to do actual transactions if they had attempted to do so. At any rate, Visa contends that that would not have been possible. (See the question "Can a fraudster with a bogus contactless terminal steal money from my card by brushing up against me?" in that FAQ.)
In sum, the technical risk re. stealing payment card information or successfully doing phony transactions seems to be low-to-nonexistent in the usual contactless payment card implementations. However, if you really, really want to be on the safe side and it would make you feel more at ease you probably could inconspicuously put some metal foil of some kind in your wallet, purse, or other card-carrying device. Save the $25.00+ that some of these ads are quoting to buy products that consist of something more than small pouches made out of 10 cents worth of aluminum. :)