Quad-Cores are still in the minority as far as most people's systems are concerned. The general public is only now starting to move to dual-core, never mind anything more than that. So it's not necessarily in a game developer's best interest to code with quad-cores+ in mind. If any issues that may result are as easily fixed as adding a line in an ini file, that might very well be enough for them.
If any possible issues can be fixed by adding a line to the ini file, you'd think the programmers might make the minimum effort to have the game detect a quad core and make the necessary change to the ini file itself. People may be unaware of WHY they are having a problem. Expecting customers to troubleshoot what is a simple fix for the developers is just poor form.
Also, quad cores may not be common amongst the general public, but according to Valve's hardware survey they do on a regular basis, more than a quarter of PC gamers use a quad core. Those CPUs have been available on the market for three years now. Developers need to start adding support for them - there is really no excuse, as doing so will future proof the games as well.
It is the same thing that annoys me with some software developers' seeming refusal to support a 64-bit OS. RAM is now cheap and plentiful, and a 32-bit OS literally can't use more than 4 GB of it. And an operating system like Windows 7 uses up to 2 GB of that RAM for itself - locking you at 2 or less for games or other applications. 64-bit OSs have been around for years now, and I have one, because I need it to use the 14 GB of RAM in my system. No game uses that much, but am a digital and 3D artist, and programs like Photoshop and 3ds Max make use of it - not to mention it lets me multitask with several open programs at once. However, I have to keep 32-bit versions of those programs installed on my system, because big name companies like Nvidia and Adobe won't port or update some fairly essential workflow plug-ins and tools to work with 64-bit versions. A shame, because, according to Valve, 36% of PC users are using a 64-bit operating system.
So I just get tired of the seeming developer laziness in refusal to put forth the extra effort to support technology advances that were made half a decade ago. It impedes my professional work, and annoys me when it impedes my gaming as well. I shouldn't be penalized because my PC outstrips recommended requirements. Many developers seem to be ignoring a third of PC users - I just hope Obsidian is not one of them.