With an international language certificate on your CV you will always have a plus in the job market. Also, if you want to study abroad, an international language certificate is a mandatory requirement of acceptance for most foreign universities.
Due to the very specific questions they contain, it is difficult to pass an internationally recognised language test without a special preparation. During an exam preparation course, you will practice specific strategies and procedures for the language tests you are going to take and acquire the corresponding language skills in order to improve your chances to effectively pass it.
One of the main advantages of an exam preparation course is that the teachers know the specific contents, goals and requirements of approval for the exam you are preparing. This allows them to be able to help you individually and focus on the speciffic aspects of your linguistic knowledge you need to improve in order to pass the exam.