Why isn't phonetic spelled the way it sounds?

Answer: "phonetic" is an alphabetical representation of the Word phonetic.There could be a phonetic representation of the Word phonetic as /fəˈnetɪk/.The users of the language English have agreed upon the spelling system they have today.However unscientific, fraught with bizarre rules it might be, it is part of the agreement of the users of that language. The same should apply roughly to all spelling systems. Yes, including devnagari spelling systems as well. No spelling system can be expected to be faithful to the exact pronunciations. That is how the facts are.