Integration
Depending on the manufacturer and the price category, modern motherboards offer quite a bit in the way of extra features. For example, an integrated NIC, USB and on-board sound are pretty much standard fare on today's motherboards, while some manufacturers offer even more features, such as card-readers, RAID-controllers, etc.
For years now, certain elements within the industry have been ringing the death toll for graphics cards. According to this rationale, integrated graphics will supplant the add-in graphics card. As is often the case, things look slightly different in practice. As already mentioned above, modern 3D graphics require an enormous amount of processing power and very high data transfer rates. The transistor count of current 3D graphics chips already surpassed that of CPUs a few generations ago, and the memory bandwidth of graphics cards is much higher than anything that a PC's memory bus could offer. All these factors make the production of graphics cards a complex and expensive proposition. Therefore, integrating such a high-powered graphics chip onto a motherboard is rather problematic, due to incredibly high costs.
