As users do not add artists to Roon, they usually add pieces of music - maybe streaming services allow users to directly add Artists to Roon but I’m not sure as I don’t use them, results of such a hypothetical sort would possibly be unexpected and without any real value to users - or limited to users of streaming services and artist directly and explicitly added through said streaming services. For users owning already a big library as they started out with Roon, only a few (handful, dozen) Artists might have been added in the years after the initial import of the library. For me it’s hard to see a value for such a sort option.
If Roon Labs wants to implement that somehow, fine with me - nobody has to use it just because it’s there.
Further read: