Rating agencies, Markets and Psychology

If the rating agencies merely state an opinion about the financial health of a company or a country, why is that investors credit their decisions so vehemently?

1- the rating agencies do not emit merely opinions; and/or

2- their decisions are only opinions when they lower ratings or when the ratings are proved to be inaccurate; and/or

3- investors don't trust other sources of information; and/or

4- investors assume an opinion as a short term determination rather than an information provided to understand a larger picture; and/or

5- self fulfilling prophecies are fed by opinions, not by facts; and/or

6- the so rational financial markets are incredibly permeable to group dynamics and structural psychological processes of decision-making deviation.

I still believe that Psychologists and Sociologists should play an important role in the big financial houses of investment, as well as in the rating agencies. They would provide alternative frameworks of understanding, much more solid and sensitive to the full range of psychological and social dynamics that are formed in the society in a particular context.