Because fuck it
Just this single reason should be good enough for a person to stay away from voting. I don't see any reason why I should follow the mindless crowd. It's not like bunch of people I don't even know outsmart me merely just by their quantity and therefore I should adjust my actions according to theirs.
I remember, every time I did something stupid because some of my classmates did it first, I was always told by my teacher the following:
If someone tells you to jump off the window would you do it?
I don't like schools, I think they are worst prison camps ever invented but this is probably the most valuable thing I've learned there. To me it just doesn't make sense to jump on the bandwagon with brainwashed sheeples, even though they are the majority and they think that simple fact makes them right. No, it doesn't.
It's been proven by history that making circles on a piece of paper and stuffing it into a "magic box" won't solve shit. Quite contrary. It will more often than not make things even worse. As far as I know Hitler was elected in democratic elections. And then, with blessings of millions of voters, it got nasty. If it wasn't for voters, he could still elect himself but would he have any real power backed by masses? I don't think so.
People also complain about banks and large corporations stuffing politicians' pockets with money to pass desired laws. A voter is basically trying to change the corrupt system by using tools of the exact same corrupt system. But where's the logic in that? I'll tell you the secret - there is none.
Rights you don't have can't be delegated
Voters always like to say things like "I'm giving a politician power to do X". And politicians then gladly abuse it to steal your money (taxes), kidnap you (put you in jail) if you refuse to "pay" and even murder you if you dare to defend yourself and your private property.
But think about it a little. Where does this power come from? Do you poses a moral right to steal, kidnap and murder? I think everyone knows the answer. Then how come you can delegate these rights you don't have to someone else?
Based on the above premise it's quite obvious that such action is immoral (and illogical). I'm pretty sure most of you wouldn't steal from your neighbor let alone kill him, yet you think it's perfectly fine to hire some armed thugs in costumes (cops) acting in the name of "the government" to do it for you. I bet you can't even explain this shit.
I'm not a democrat
I simply don't believe in democracy. The system is corrupted by it's definition and what's worse, it makes natural enemies from people that would have otherwise gotten along just fine. Voters of a party X hate voters of a party Y and they all hate those who don't vote.
I hate you all, but not because of your political preference. I hate you all because you're all stupid and violent animals. And that's probably an insult to animals.
It's capitalism (free market) on the other hand that makes natural allies and promotes peace and prosperity. It's the only "system" where people with different opinions freely and peacefully trade with each other (mostly) without any prejudices. You go to a store to buy milk and you don't give a flying fuck if the person behind the counter is short, fat, or has a different amount of melatonin in their skin. You are driven by your selfish needs and wants and the most important thing at that particular moment is to trade your money for the milk.
Take another example. The US government (and not just them) hates China and spreads all kind of propaganda so does the Chinese government. Yet they are the biggest trading partners in the World. Millions of Americans use Chinese products and tens of millions of Chinese got out of poverty because of this mutually beneficial transaction. This has happened not because of democracy, but because of capitalism and the ability to trade with your fellow men.
I've given an example of democracy before, but I'll say it again - Hitler. You can see brutal examples of democracy in not so distant history too. Starting with governments bombing the shit out of other countries, ending with violence on its own citizens. All democratically approved by you, voters.
However what is more interesting than your vote insignificance is the fact you can't make any reasonable decision in this game. There are tons of political parties scamming you into voting for them which makes it impossible to go through their programs, promises, past actions, past inactions etc. The combinations are endless and even if you could thoroughly analyze all possibilities and choose the least fucked party, making assumptions mostly on their current promises is far from being reasonable.
As far as voting in Slovakia goes (but I'm pretty sure it's the same in most countries) you can't elect politicians across the whole political spectrum. You have to stick with politicians in one party instead. The chances of finding numerous honest politicians in a single party are next to none. You're then only left with an option to vote for the whole corrupted group of sociopaths, or to not vote at all.
If you're against evil then your only option is to stay home on election day and do as you do every other day. After all, it's a day like any other.