That is because modern English is a (pardon) bastard language which has diverged greatly from even her sister languages. For example, Islandic, Faroese and German still assign 3 genders to and declinate "the" (der/die/das) with clear pronounciation, partially also true for Dutch.Eh. Very common instinctive mistype. In latin derived languages the sound 'the' would be written 'de'. Actually the english pronunciation of letters is rather weird, not to mention inconsistent
And English pronounciation is a chapter all for itself, even the British admit that their spelling rules are a headache. This contrasts obviously with the other Germanic languages, who all have rather consistent rules. e.g. it is near impossible to mispronouce a German word you read in a text, if you know just a minimum of German spelling.