purpose of an English test is to assess a person's ability to communicate in English

It seems that if the purpose of an English test is to assess a person's ability to communicate in English, whether it is verbally or in written form, the IELTS test provides a much better reflection of this. If you are an English learner and you are investing your time to learn the language, then surely it makes sense to take an exam that more accurately reflects your level of achievement and also that motivates you to learn the language in a meaningful way that results in communicative ability. Preparing for exams like the TOEFL, motivate you to spend endless hours trying to learn lists of vocabulary and grammatical points, which don't necessarily lead to significant benefits in being able to hold down a conversation or write a college essay.