Question on PingFederate

[It Meme]

I know this is not the forum for PingFederate but with many SAML gurus
here, the feedback will be good.

Our institution is considering implementing PingFederate as an IdP.

Ping recommend using the following as SP options:

1) Open source SP (e.g. Internet2's SP)
2) PingFederate (PingFederate can run simultaneously as an IdP and SP)

Ping mentions that the same instance of PingFederate can run both as
an IdP and SP - I am curious on what would be the use case? Won't this
defeat the purpose of using SAML?