The simple answer for the first two is that there is no particular reason. In English, we use 'about'. If you used one of the others, your idea would be understood but the impression that people would have of your English ability would be lower. In many cases, that doesn't matter very much as long as you are understood. 'For' changes the meaning. What is good for this job? = What does this job need? For example, what qualifications are good for this job? What kind of person is good for this job?