Retroviruses mutate relatively rapidly. what is one of the reasons?

Retroviruses store their genetic information in molecules of ribonucleic acid (RNA). However, unlike other RNA viruses, retroviruses use RNA as a template for forming deoxyribonucleic acid. Viral genetic replication, especially in the case of retroviruses, have few, if any, error-checking mechanisms, which results in a high rate of mutation.