Because pretty much no language besides Latin actually maps nicely to the Latin script. Pretty much all languages use digraphs, diacritic symbols or completely new letters in the Latin script (even English, œ and æ, for some time at least).
Having latin alphabet with diacritics and digraphs is still better than something like Arabic. Some non-latin alphabet with letters separate from each other (like Greek, Cyrillic, Armenian, Georgian, etc.) would be fine too.
Having latin alphabet with diacritics and digraphs is still better than something like Arabic. Some non-latin alphabet with letters separate from each other (like Greek, Cyrillic, Armenian, Georgian, etc.) would be fine too.