No offense, but I think that's a very western-centric view. Your example only make sense when the user is familiar to English (or other western languages, I guess). To me personally, I find it strange that "D.txt" and "d.txt" means the same file, since they are two very different characters. Likewise, I think you would also go crazy if I tell you "ア.txt" and "あ.txt" means the same file (which is hiragana and katakana for A respectively, which in a sense is equivalent to uppercase and lowercase in Japanese), or "一.txt" and "壹.txt" means the same file (which both means number 1 in Chinese, we call the latter one literally "uppercase number")