Have you ever opened a code file two years after running an analysis only to find that you have no immediate memory of what it does?
Have you received analysis files from a collaborator with meaningless file names like analysis_1final_FINAL.R, or variables named x1, x2, temp?
Consistent code styling makes your research code easier to read, maintain, and share with collaborators. Well-formatted code reduces errors and makes it easier for others (including your future self) to understand your work. This is an important aspect of information management in collaborative research projects.
Conventions and tools to improve code quality are discussed in detail in Code Quality in Guide for Reproducible Research.