Because it's the cheapest they could go with.  Cooling the memory isn't necessary in the R13.  Why do you need to wear hand gloves?  
Hiya Y'all, I use an Aurora R13 with GDDR5 4400 32 GB memory. I can remember an Aurora R3 from 11 years ago had cooling on top of it. And those 2 banks had top end blue anodized heatsinks. Now I bought an Aurora R13 and look inside, there is no any cooling information about memory, no top fan, no heatsink or whatever, just a plain top of the build memory, why? I created 4 top ends for those 2 modules because its plain at sight. You need to wear handgloves to remove them. That cooling bring down temp with 23%. So I create 4 top ends with a tolerance 0,05 and a 45 degree mill, and cut 0,02 to pull off, pull on. So my question is why did Alienware put 2 memory chards plain into slots without cooling?
Aurora R13, cooling GDDR5 4400