why do you say that?
The relationship between a letter[0] and the sound is entirely arbitrary - I could write 'A' and pronounce it as 'T'. Why would one set of charcters be less fit than another?
[0] or symbol, more broadly eg. in welsh 'dd' and 'ff' are letters, even though 'd' and 'f' also exist in the alphabet. And in english we have sounds not represented by a single letter eg. 'th' sound
Because one might already have phonetics associated with it. I literally have to read out messages aloud, have my wife read aloud other parts of the message so we can figure out what the sender meant. My favorite is a Berber from Tanger: amazight, arabic, spanish, some french, no formal education but also no inhibitions to write...and all in one alphabet. The only way to understand the text is to read it aloud once for each language, mark the parts that make sense in o e of the languages and then assemble all findings...