I don't see a reason to doubt cooling benefits, but on PC DRAM, the advantages of having such cooling is minimal. Regular DDR4 modules without even a simple heatsink is fine for them.
When efficient blue LEDs were thought of a few years ago, companies started plastering electronics of all sorts with blue LEDs everywhere. We still have speakers that use such blue LEDs for an indicator light. It's annoying as hell, because blue is one of the colors that's particularly bothersome to our vision, but they did it, apparently to reduce costs by mass producing it.
(BTW, any geniuses thinking of using blue LEDs as an indicator light for their fancy electronics project, DON'T! Use green, which is pleasant to see, heck red wasn't too bad. Blue just makes me want to smack people. Blue LEDs in christmas time makes the entire house look blurry)
Back to the point. It's an offshoot of the RGB LED rage. Apparently we are suckers for shiny things, so everything with LEDs on them makes it more attractive to buyers, allowing sellers to overcharge for them. PC markets are very low margin, so manufacturers will jump at any opportunity to sell higher cost items.