Light Propagation Voumes - when to use?

Both the tutorial I watched and the documentation explain the What but not the Why.…mes/index.html

My understanding is that LPVs have very limited use case when you are using a dynamic sun.
And lightmass, precomputed GI has to be disabled.

So why would you every use this feature?

Seems like you answered your own question… It provides fully dynamic GI, where as indirect lighting from lightmass is completely baked into the scene.

If you need fully dynamic GI, then it is essentially your only option (with SSGI, but you should probably be using both at the same time)