Publishers' policy, Fund. Following

Most of publisher are making money for access the research article.

Money is the major reason. Come to think of it, some journal publisher charge as much as $30 to have access to PDF document of such paper.

MONEY! the country of origin, all the differences that exist between us, and which are not spoken out loud!

Following answers.

What kind of research do you mean Dear Sir?

Unfortunately, it's for economic interests

The main problem is that many publication companies are established for profit. Therefore, they charge a certain fee allowing us access a specific publications.