Except that is not true, it is sometimes convenient, and sometimes very inconvenient and not wanted. My reasoning for file systems that are case sensitive is the following:

1. Some people want file systems to case sensitive. 2. Case sensitive is easier to implement. This is very much not a trivial thing. Case insensitivity only really makes sense for ASCII.

In the camp of wanting case insensitivity:

1. Some people want file systems to be case insensitive.

There is more in favor of case sensitivity.