Its political importance is based on the following scenario. At the time the Phalanx came into being, Greek cities contained a mixture of wealthy, poor, and those rising in economic status -- an emerging middle class. Ruling kings realized that they could build an army around larger military formations because more men could now afford to buy the necessary equipment. We can only speculate about the chicken and egg here. Did the kings coerce at first and then later the hoplites figured out how to leverage political power, or did the hoplites refuse to fight unless they were given political rights? I suppose we can imagine a case where the initial formations were small coerced units which grew in size when more independent men decided to participate.
Accurate data pinpointing the advent of the Phalanx is elusive. Written evidence is non-existent so we have to rely of archeology to guide us. The following image, referred to as the Chigi vase, dates from around 650 B.C.