Also imagine having two files in the same directory which differ only by case. What would be the benefit of being able to have two or more such files?
Are there any use-cases for which case-sensitive file-system is better than case-insensitive one?
Actually, not having the exact file may not provide a utility for you, or most of us, but searching for a file in a case sensitive manner, and getting ENOTFOUND just because it doesn't present in the way I searched is valuable from my point of view.
Also, having a case-sensitive system is simpler from technical point of view, and prone to less bugs. This is especially true after UTF-8 become ubiquitous. Searching for an exact byte stream is much more simpler than a country dependent, exceptions filled search/match algorithm.