The interesting situation is that there is no real debate which of the formatting styles is better. Other problems in typography can be discussed but everybody knows that it is offtopic to question the idea of justified text. The reason is that the problem of arranging words on a line is seen as equal to typography in general. That means typography is about justified text.
Nearly all the professional books and journals in the last 400 years were printed with justified text. This sounds incredible because in the past no software was used but mechanical typesetting machines. But it seems that the machine experts in the past have solved the problem of word justification over a line. The standard mode of the monotype typesetting machine was that it has procuded justified text and nothing else. The only question which was asked is how to realize this formatting style.
From a technical perspective it is possible to create left justified text with the monotype typesetting machine. And technically, the LaTeX software can do the same for an academic paper. But in the reality nobody is doing so.
To understand the situation we have to go back 100 years and take a look what a human operator at the monotype machine was doing. He gets a manuscript which was either written by a typewriting machine or by hand. And the objective is to convert this manuscript into a justified text stored on a punch tape. The idea behind the monotype machine is to justify the text. This is realized by counting the words, and measuring the spaces, and then the amount of free space is determined. This procedure is repeated for every line.
The interesting fact is the formatting style “Justification” is only one possible formatting style. The text can be read also very well if the step is missing. So why is this step done? Mostly because of tradition. THe idea is that the text is so important and will reach so many readers that the typesetting has to be made with the highest possible quality. And this is equal to fully justified formatting.
This self understanding sounds similar to how books are created before the advent of printing machines. The idea was, that the content of a book is so important that it has to be copied by hand. Creating a copy by hand takes longer and this shows the reverence for the content. Bascially spoken, creating a copy of book by hand is more costly than using a printing press. And creating fully justified text is more expensive than creating only left-justified paragraphs.
Left justified text means basically to lower the quality of typography. Let us make simple calculation. What will happen if the monotype machine is used to create left justified text? Right the duration for typesetting the document is shorter. The human operator needs to calculate less and he can typeset more manuscripts in the same time.