"Normal forms" are definitely a thing, most clearly in linear algebra but certainly elsewhere as well. Being able to normalize any description of an object to a single unique canonical description is incredibly useful!
But we don't always want to work with normal forms, for one reason or another, and there can be multiple kinds of normal form to choose from depending on your needs. For instance, if you do anything with something in a normal form, chances are it's no longer in a normal form! The lack of closure properties like this means you may only normalize at the very end of a series of manipulations, during which you're using a more suitable notation.
But we don't always want to work with normal forms, for one reason or another, and there can be multiple kinds of normal form to choose from depending on your needs. For instance, if you do anything with something in a normal form, chances are it's no longer in a normal form! The lack of closure properties like this means you may only normalize at the very end of a series of manipulations, during which you're using a more suitable notation.