In societies that don't, it cannot be taken for granted. The real political problem in our world in the next 20 years is that most human births will tend to occur among the poorest sectors of the world and in the poorest sectors of the richer parts of the world. That means that while middle classes increase in absolute terms, in relative terms, middle classes are either staying the same percentage of society or getting smaller, which does not bode well for political stability. What I see ahead in the coming decades is a return to what the ancient Greeks called hybrid regimes, or mixed regimes. In other words, a regime that mixes elements of democracy and elements of military or oligarchic business rule in various combinations.
Turkey is officially a democracy.
You cannot be a member of NATO unless you are a democracy. But in fact the military plays a very large role in daily Turkish political affairs. The key political institution in Turkey is the National Security Council, not the parliament. And in the National Security Council, the generals come with dossiers with which to lecture and the civilian politicians come as tourists in order to listen. Peru, is another example of a mixed hybrid regime, where you have a leader who has been democratically elected twice, but has done away with many constitutional imperatives, and basically governs through the security services.