The core of Democracy is based on two propositions:
One is a moral belief that, it is just that people govern themselves, rather than being governed by a special person or group.
The other is the pragmatic fact that granting power to a special group or person inevitably results in those with power often doing what is in their best interest, even when it conflicts with the interest of the rest. In a democracy the people, not a ruler (even an elected one), are supposed to be the ultimate “Decider”.
Because Tribunes are selected randomly from all the eligible citizens willing to serve, they do not start out as a special group. Because Tribunes have a short tenure, are dismissed after voting, and retain no special rights, they do not start out as, or become a special group.