Because it still helps and if the core is hot the heat is spread around thereby heating up the memory. So yes it does help. In low power GPUs it would be cosmetic but higher ends cards should have it. It won't make a massive difference but keeping cooler for longer just extends the life of the card.
Don't mention to Chrazey anything about repainting... he will spend the next 6months looking for an entire cooler in a different colour rather than repainting
I haven't had a graphics card with memory modules on the backside of the card in ages. Sure Titan models have that, and some others. But it's certainly not 99% of them.
Cosmetic or not, it surely doesn't hurt to cool the VRAM for overclocking purposes. Why else would anyone buy these custom cards?
Define cooling? in some cases metal back plates actually make the ram hotter because they trap the heat in and prevent it being shifted.
The issue is they can not, for obvious reasons, stick heatsinks on the ram on the back of the card because then it doesn't meet spec and you can't actively cool it either.
Thing is heat is not the deciding factor in ram clocks. So that's why heatsinks are a waste of time, they're usually mostly cosmetic.