It's not "bad" per se, but the history teaches us that governments that do not share the values of personal rights and freedoms very soon devolve into the governments that are treating their citizens very badly and the citizens themselves are living very poorly. It also happens very frequently that while initial consent may be given by democratic means, very soon such consent is not required anymore by the government and it usurps the power completely and does not let the citizens to dissent and choose better government anymore, instead forcing the citizens to accept the fruits of their poor choice in the past forever, or at least until they can overthrow such government by violent means.

>>> Shouldn't the 'voice of the people' be of enough value?

Not every "voice of the people" has equal value. For example, if 100 years ago in the US white majority would vote to keep black people in slavery, would we now recognize this decision as good and legitimate? What if there were a country somewhere else right now that has majority oppressing the minority and denying them their rights and freedoms? I think we would consider it "bad", despite formal requirement of "voice of the people" being satisfied. That's why, I think, USA is a republic, and while Americans elect their leaders democratically, there are limits to what "voice of the people" could do, at least until current system of government persists.