Why did Ridge Racer disappear?
A combination of piss-poor quality Ridge Racer games from Namco and the onset of Forza Horizon (and before that, Test Drive Unlimited 1 and 2) taking over arcade racing, but with an increased scale, sandbox gameplay, and online capabilities, did Ridge Racer in. Before Forza Horizon, the Project Gotham Racing series of games also stole Ridge Racer's thunder, especially PGR 2 and 3--those were straight up track-only arcade racers that had polish, excellent online play, and imagination--all things the last Ridge Racer games failed to have.
PGR, Forza Horizon, and Test Drive Unlimited are arcade racers but with real vehicles. Plus PGR and Forza Horizon are every bit, if not moreso, scenic and graphically captivating than anything the Ridge Racer series brought to our screens.
Instead of lamenting Ridge Racer, we should be lamenting Activision killing off PGR.