I'm in the middle of adding the catalogue of an online artist who's gone through three aliases since they started. It makes sense to have every name associated with the same entity, but since they don't use their legal name on their music, I want to carry the distinction of what period they released some recording in (as reflected by what alias they used) through the releases, recordings, "performer" credits, and works. The first two are easy enough, but the relationships being added seperately means I wind up typing the alias about three times for each release -- and since they use the Soundcloud/YouTube model of releasing individual songs rather than albums, that's a lot of releases. Yeah, I might be able to copy it rather than typing it out each time, but because I'm adding URLs I'd need to store it in another window (by which point it's not too much longer to have typed it), and that wouldn't help making sure I didn't forget an AC field.
Replace "alias" with "legal name" in much of that, and the task is pretty similar: if the entities are merged, you wind up needing to type one name into the AC over and over, hoping your fingers don't slip on the keys (or else greatly increasing your mouse's travel time) and that you didn't skip changing a field. If you're working with artists that have any real hope of being edited by anybody beyond you and the artist themself, you also have to hope those future editors will also add the proper AC rather than just linking the entity. The artist's legal name may even include Unicode characters, making everything all the more difficult. On the other hand, if the legal name is a separate DB entity, all you have to do is link it and you know -- barring shortened forms -- that it will be displayed correctly.
That's deliberately an overly-bleak picture, and I actually tend to be on the side of merging if the legal entity's not all that notable in the database, but I wanted to present some of the considerations that should go into merging the entities. Yeah it can all be covered by our systems, but that doesn't mean the editing process is the same.