The relational database model gained popularity and many proponents during the 1980's and 1990's, a period of time in which IT organizations were seeking to consolidate data from multiple individual information systems into a single data repository which could then be accessed by all of the company's application systems. Keep in mind that this was before the trend toward Enterprise Information Systems (EIS) in which the applications themselves were also brought together under a single umbrella in a comprehensive system such as SAP as done. Relational structures were widely discussed and analyzed, raising relational methodologies to a high degree of development, and almost all major systems included relational database technology.
Since that time, other database models were introduced, most notably the Object Oriented Database Model, which provides an excellent tools for modern businesses.
However, it seems that, up to the present time, the relational model continues as the most prominently used database management tool. Any thoughts about why companies have not moved in significant numbers toward new database models?