Investment houses do. They are bound by laws in various countries. If a certain organization or country has been declared junk status, investment portfolio managers are not allowed to invest their clients' funds in any such organization or country. There are criminal consequences for these investment houses if they ignore the rating agencies. That being said, most investment houses only make use of Fitch and S&P and ignore Moody's.I don't think any of these agencies really even matter or anyone takes them seriously. Just look at their history of being wrong all the time.