Formal literature reviews may also get considerably over-extended by modern university practices.
It summarizes the current knowledge of the subject and highlights its crucial features, pointing out its main issues, such as recent findings, trends, etc.
If your paper is an introductory part of a thesis, it must be focused on a central argument that supports the idea of your research.
Hence researchers tend to be highly averse to repeating or renewing them — indeed with some systematic reviews the design may mean that ‘topping up’ at a later stage is not feasible.
Yet over the course of a research project (and perhaps especially in a Ph D project), the analyst’s understanding typically expands hugely.