NBGI themselves wanted to get away from the franchise as possible.

Old Shame: After recent releases such as the cancelled Drifttopia and the mobile Slipstream, there are no news regarding Ridge Racer franchise, since Namco pretended that Unbounded, the Franchise Killer, never appeared in the series.

In contrast, the Critical Velocity, Pachislot Ridge Racer and Accelerated are exclusively sold in Japan. The latter could also apply to Ridge Racer 64, with 64 being the first Ridge Racer title not to see a Japanese release. Inversely, Ridge Racer Unbounded was released in North America, Europe, and Australia, but not Japan. It is also the last installment for the home consoles in the Ridge Racer series. This is the first Ridge Racer game with destructible cars and destroyable scenery which is similar to Burnout and Split/Second. Created for Windows, Playstation 3 and Xbox 360.

No Export for You: Ridge Racer 2 on PSP was released in Japan, Europe, and Australia, but not North America. Ridge Racer: Unbounded was created by Bugbear Entertainment and published by Namco Bandai.

Name's the Same: There's a special car in the series called Angelus.

As such, it became a Japan-only title from then.

Denial of Digital Distribution: Drift Spirits was pulled out from the non-Japan stores and their servers shut down in 2016.

Ridge racer unbounded pc wikipedia