It's called future proofing Soar.
As the 64 bit platform develops, more 64 bit programmes will become available that will utilise all of the available RAM. At the moment, 64 bit programmes are a little limited but, for example, I run Adobe Photoshop 64 Bit and would really benefit from 16 Gig of RAM. Also I use the 64 bit version of Steinberg's Cubase and the more virtual instruments and effects I employ the more RAM I need.
Even though you may not feel the need for such a lot of RAM, as DM says, the price of investing in a 16 Gig kit is now reaching the sweet point and it is something that really is worth more than a passing thought.