Ah. In essence, USD is really just a interoperability file format. So it exists beyond Solaris, which is a bit of a bold move to be honest. Solaris being married to USD on the get go.
Much the same with with OBJ, FBX and Alembic.
So if you are already fine with those format then there is probably no need to go USD.
Just a brief progression, those formats was created because there was lacking in the formats before it.
For example, OBJ was used simply to transfer 3D model but then it can't really carry weights/animation etc.
That's why we have FBX. FBX works but it still has to interpret some assumptions (such as joint order rotations, hierarchy, how an object in DCC A is read in DCC B).
That's why we have Alembic (developed by ILM and Sony). It's a cache format. So there's little interpretation and assumption. It's really just a point level animation.
So USD developed by Pixar is like Alembic, where it is cached but its not limited to just files. It's also file management, hence medium-big production gets more mileage to it.
"scene description" is not a new thing. Every DCC has its own scene description. Maya has it. C4D has it. Houdini has it. It's when you render stuff where the DCC collects the objects, materials, lights before calculting the pixels.
I guess the clearest thing about USD vs Alembic is USD can contain another USD (i.e. part of "file management)". Alembic can't contain another alembic (AFAIK).
The unique thing about this one is its goal to be "universal". And that's why people gravitate towards it especially that a 3D artist in a production environment doesn't just use one DCC. I mean any format wants to be universal for sure lol but since USD has been tried and tested on production (i.e. Pixar). So in essence, it could be any format really. It just so happens, Pixar was forefront to it.
That aside, another reason to use it is relatively faster than all other formats. Faster to read, to process. Etc.