AA batteries are mainly useful (anymore) for childrens toys and flashlights given the proclivity of manufacturers to make rechargeable batteries part of our multitude of consumer electronics. OTC meds are only useful if you are sick. Razor cartridges are only useful for specific razors.
As I said, pretty much EVERYONE needs laundry detergent and needs it every couple of months. Find another product that fits that description and you may have a point. (And is also a product that does not spoil quickly.)
It very well could be just a fad, but it is an extremely logical fad if it is.
Laundry detergent is only "necessary" if you want to wash your clothes, and if you want to use some kind of soap, and a soap actually made for that purpose. If you're buying your detergent on the black market, how concerned are you with such things? I don't know.
Small batteries and OTC meds are about that "necessary" and also last a while. Small, lightweight batteries are used in a number of things besides toys and flashlights. Things essential to people who buy their detergent from the trunk of a car. Things like remote controls and cell phone chargers.
On the razors, yeah, you have a point. Of course, it depends on how many regular clients our household goods black marketeer has, with whose choice of razor he is familiar. I can't believe I just typed that last sentence, but I also can't believe we're discussing Tide theft rings.
I think it's this.
Someone else stole Tide, so someone else did, and someone else... Essentially a ghetto-fad, with no more real reason behind it but "just because". The same way gigantic chrome spinny-rims on cars or pants you wear halfway down your thighs, and have to hold up with one hand are popular.
That would explain why that brand is being targeted. If the explanation were all that pragmatic, there should be other brands disappearing from the shelves, or at least the big names.