Why Selenium RC is used?

Selenium-IDE does not directly support:
1. condition statements
2. iteration
3. logging and reporting of test results
4. error handling, particularly unexpected errors
5. database testing
6. test case grouping
7. re-execution of failed tests
8. test case dependency
9. capture screenshots on test failures
The reason behind why Selenium-IDE does not support the above mentioned requirements is IDE supports only HTML language. Using HTML language we cannot achieve the above mentioned requirements. Because HTML does not support conditional, looping and external source connectives.
To overcome the above mentioned problems Selenium RC is used.
Since Selenium RC supports the languages .Net, Java, Perl, Python, PHP, and Ruby. In these languages we can write the programme to achieve the IDE issues