Why are hereditary leaders so frowned upon?

Why are hereditary leaders so frowned upon?
I can understand if it's in a dictatorial way, but nowadays some people take umbrage when some leaders' children or relatives take their place in political position.

Some people raised a stink when I won the election for mayor last October, because my grandfather had been mayor for almost 40 years in separate terms before the government put term limits - plus it was a democratic election, not a handover.
Why are hereditary leaders so frowned upon?
I considered suing a person because she spammed the comment "The dictatorship goes on" on Facebook when I won the election, but now I get ironic and say to such people "True, for now and the next forty years!".
I think that hereditary leadership is not inherently negative, and on the contrary, can provide continuity and stability.
Thoughts?
Why are hereditary leaders so frowned upon?
Post Opinion