Why wouldn’t they still exist? Because they faced many hardships as well as temptations to change.
Shortly after the schism, the Old Believers were persecuted; some were imprisoned and others were burned alive. Many Old Believers fled to remote villages in northern Russia or to Siberian wastelands and established tiny settlements. In these areas, they remained isolated from greater Russian society until Tsar Nicholas II proclaimed the Edict of Toleration in 1905, releasing the Old Believers from exile and persecution.
The Russian Revolution in 1917 led thousands of Old Believers to flee military conscription, religious persecution, and starvation in the new Soviet Union. Some traveled to China and built colonies and farms in Manchuria’s Three Rivers Valley. At the beginning of the Cold War in the 1950s, communist pressure forced these Old Believers to emigrate from China and remote Soviet villages. They assembled in Hong Kong and at western Soviet ports where religious and social charities helped them find land in friendlier countries. A sizeable number settled in South America—particularly in Brazil. However, life was difficult in South America, thus many emigrated to the United States in the late 1960s. Here, in Oregon, they found life easier but also more tempting for their youth, so hundreds moved to isolated areas in Canada and Alaska.
Sometimes, in history, persecution of isolated Christian communities (Albigensians, North African Christians, Nestorians and Monophysites in Central Asia) resulted in their disappearance or move to other areas where survival was still not easy. It remains to be seen if greater religious freedom along with increasing secularism and materialism will assist or hinder the survival of the remaining Russian Old Believers.