Because Intel told them for years nobody needs more than 4 cores, and the majority of games, even today, don't really benefit from having any more than 4 cores. 4 cores and a high clock speed would be better, right now, for gaming, than 8 cores at a lower clock speed. That being said, I use an 8 core CPU that works quite well for multi-tasking and gaming, and I see 8 core CPUs becoming the new standard in the next couple of years.