If you book with a larger studio then the actual photographer on the day might be picked from a pool of potential people, often called “associate photographers.”
This type of arrangement may be fine for you, if the studio has a particular “house style” that you like.
But some wedding photographers operate as a single person, or a married couple. These are great if you’d like to guarantee who will be shooting your wedding.
It may be that you’ve fallen in love with a photographer’s style, or you develop a great rapport in the months leading up to your wedding, and don’t fancy meeting someone completely new on big day.
So it’s worth asking exactly who will be shooting the day.