Why did Matthew and Luke include such long genealogies in their gospel accounts?

From their earliest days as a people, the Jews considered their ancestry important. They divided the promised land into tribal areas, and within those areas were towns and villages that belonged to certain families who owned land there. Every fifty years the various lands would revert to the original owners, so genealogies were very important.

In addition, these careful, detailed records of their family histories enabled each man to identify his father’s home area and go back there for official obligations such as Caesar Augustus’s census.