"I have never had any issues with large files" does not equate to "there are never problems with large files." Your lack of experience with such issues only indicates that you haven't encountered them, not that they don't exist. For example, I have had to work with text-based log files exceeding 2GB back in the x86 era, where RAM was limited to 4.2GB (including the OS). Handling such large files was nearly impossible, rendering them useless for troubleshooting purposes. The simple answer is that performance is impacted by file size once it reaches a certain point. As a basic illustration, how would you efficiently look through a file larger than your machine's RAM? While a 10MB cutoff may seem low, it is likely chosen to ensure the file remains manageable for manual review and scrolling. We can debate what a more appropriate limit would be, but it is clear that setting a size-based cutoff is necessary to avoid the problems associated with excessively large files.