A dedicated graphic card usually doesn't use up any portion of ram, but a integrated graphic card needs fron 1Mb to 512Mb of ram memory, aside from the addressing scheme in a 32Bit system. The main reason to remove a PCI-E 16x graphics could be to have more PCI-E Lanes free for the storage and network controller. As I recall, a standard desktop cpu only provides 20 PCI-E lanes. If you use a PCI-E graphic card or the integrated graphic card 16 of the 20 lanes are used (or wasted) to show only a few letters in text mode. My old system was build with a PCI-E 16X graphic card, but I had a lot of trouble when I plugged in a second raid controller. After switching the graphic card for an old PCI S3 Virge card, all the problems I had with the controller disappeared.
If you look at the block diagram of my current motherboard, like most server motherboards, the graphic card is a PCI Matrox G200 graphic card with 16Mb Ram.