The International Phonetic Alphabet is a collection of about 107 symbols used to represent the phonemes or individual speech sounds of all the world's languages. Wikipedia
Since the IPA includes far more characters representing far more speech sounds than are utilized by the English language, it isn't a suitable replacement for the current English Alphabet. The characters chosen for the 7M-alphabet were selected to be compatible with the cursive writing system. The IPA never had that goal. The IPA is concerned with providing characters for the speech sounds of numerous languages which isn't the same goal as providing pronunciation instructions for the words of a single language. Many speech sounds are caused during the transition from one phoneme to another or by accents. This is irrelevant to the goal of an alphabet which only instructs the reader on fundamental pronunciation while allowing them to layer on their own personal affectations.