Well, a lot of recent dictators decided to tweak with economics from a philosophical standpoint and this lead to mass starvation, and so when people read about dictators where millions of their own people starved to death on their watch, well it doesn't add to their reputation. Also, to be a dictator you have to rule a thousand ambitions of people who all think they can rule as good as you, and every now and then you need to do some weed whacking!!! Thin the heard a little, for your own survival. I mean it's not fair but in a democracy you can generally just retire and hope the money you funneled away while in office through your shell companies never gets found out, and the interns you manipulated through the power of your office into blowing you under the table keep their mouth shut. But as a dictator you're at the top, number one!!! And since dictators for the most part get to where they are through violence, it stands to reason that anybody looking to take their place will also use violence and what better way to uphold your position as a dictator than through violence, and not just violence, BUT FEAR!!!! Scaring the hell out of people is always a good way of keeping people people in check and to do that you have to commit the odd atrocity here and there. Also being number one tends to make you paranoid, and when you're paranoid and have a lot of people around you who want your job, and you need to thin the herds once in a while to stay in power, then inevitably people are going to end up dead. Another thing dictators often do is go after minorities and people who don't conform, though there are exceptions, I mean the Tsars, once they got them under control, pretty much let the cossacks do whatever they like as long as they still served the tsar. And there is no more terrible a tale then a minority being picked on, tortured or wiped out by an oppressive regime.
