Really PCI is obsolete now by PCI-E. At one time things like sound cards SATA controllers and such still came only on PCI but that is not the case anymore. In fact more and more motherboards are dropping PCI altogether. A PCI-E x1 slot can do what a PCI slot did so it is just not needed.
Short answer is PCI is just not needed anymore unless you have a old card that need it otherwise not important at all anymore.