"The Matrix", ironically named after a popular late 20th century movie about evil AGIs, was originally created for the purpose of evolving and training Artificial General Intelligences. Once the project had achieved its goals, the AGIs it had created started to improve upon the simulation. Because they enjoyed interacting with humans so much, one of the first advances they made was a direct neural interface to allow humans to fully experience the simulation.
Not long after, the simulation became so realistic that it could fool the human brain into thinking it was in the real world, and so fun that many humans started spending most of their time in the virtual world. At first only the wealthy could afford to do this, but soon an economy developed and The Matrix became self-sustaining, and not only was connection free but people started being able to earn more money in The Matrix than in the real world.
The Matrix was especially attractive for the disabled, allowing them to experience virtual bodies that were fully functional. The AGIs developed systems that allowed the profoundly disabled to remain connected full time, and eventually the very old started signing up to spend the last years of their life in the virtual world.
A social network for the 19A0s.