For example - let say we record and mix some band album, and this band want to add other songs from a different sessions, different studio.
Always there's a problem to get some similarities in the music material due to different mikes (and microphone placement philosophy), different rooms, different drums, different backline etc. Knowing microphones used in previous session, like sm57 on a snare, sm57 on a toms, sm57 on a guitar - f**k, i hate sm57!!!!!!!!
We can easily get some similarities on instrumental tracks adding eq curves from new material. For typical recording scenario i don't see any use of it, but for some trouble situations it can be usefull.