The cycle of technology.

It seems that technology progresses in a cycle, and it usually returns to its starting points:
On older computers, parallel ports were faster than serial ports. Parallel ports were used for printers and Zip drives, while serial ports were used for mice. However, current computers have returned to serial with USB - Universal Serial Bus.
Long ago, graphics cards were PCI. Then, AGP was invented - specifically for graphics cards. Currently, AGP is being phased out and graphics cards are back to PCIe16.