We'll the Turkish i/ı/I/I is I think exactly the example I would have come up with of characters that looks the same as i/I, but should have it's own code point, just like cyrillic characters have their own code points despite looking like latin characters.
Absolutely. So i/ı/I/I do have their own codepoints. But the rest of the letters, which are the same, don't. Just like han unification. Letters which are the same are the same, and those which are not are not, even if they look pretty close.
The thing is that the turkish "i" and "I" don't have their own codepoints, it is the same one as latin "i" and "I", when they should have been their own codepoints representing the same glyphs. That way going from I to ı and from i to İ wouldn't be a locale dependant problem.
Should Norwegian A and English A be different Unicode code points just because Norwegian also has Ø, proving that it is a different writing system? You may want to debate whether i and ı should the same letter (they aren't), but most letters in the Turkish alphabet are the same as the letters in the English alphabet.