Because people can learn from other people, in both in failures and in successes. The founding fathers of the United States took after the Roman republic in modeling after there government. This is why the United States Congress is structured in the same manner as the Roman Congress. Versus the rectangular or roundtable types of congresses that are seen in European countries.
They also took after the Romans on the idea of a republic being comprised of people elected to represent them. These people are also meant to be changed out on a regular basis. And that the public was in control of who was calling the shots on their behalf.
Though the 15th amendment highlighted race, color and previous condition of servitude, women felt gender should have been included in the amendment. They helped abolitionists gain rights so they felt they should too
