Multi-Function PCIe in End-Point mode

[SNg00]

According to PCIe specification, a PCIe device may contain a collection of up to 8 functions. If a PCIe is configured to a specific endpoint, under what circumtances, it need multiple functions? Why single function is not sufficient, it is a implementation options or it is a must to have a multi functions EP in certain usage models?

Can any expert to correlate this usage models to a real life PCIE user application?

[EChun9]

An example of a multi-function device might be a PCIe card that can serve as an Ethernet Card or modem.