Sects have lost territory, been run out entirely, or never materialized in some areas. They are not monolithic and found in every corner of the World of Darkness, either. Those explored below have simply been more resilient and common.
A few have become obsolete with the advent of modern technology, for instance.
Many groups have come and go, and not all of them have made it down to modern nights. Sects are influended by era and location, as well as the popularity of their basic ideas. One of the first steps to building a character or a city is to figure out which sects are present, powerful, and open to new members. Even the most antisocial character will eventually find a reason to join a collective, if only to protect their own interests. Some are ushered into a sect by their sire upon their embrace others choose a group when they move or are released.
Their fractious nature never goes away, however, and over the centuries vampires have gathered themselves into many groups. On the other hand, they get lonely and usually find themselves drawn to others of their own kind. Vampires are often territorial, distrustful, and competitive - not exactly the best companions.