Comment by int_19h

In practice, all languages that use digraphs and trigraphs don't use distinct Unicode codepoints for them, generally speaking (and Unicode specifically marks those codepoints as legacy, so this is an officially blessed practice). The reason why they exist is because one of the explicit goals of Unicode as originally designed was to be able to roundtrip many existing national encodings lossless. So digraphs that were already in the national encodings for whatever reason ended up in Unicode as legacy, while those that were not, did not.