1: It takes time and effort.
2: The odds of it making a difference in the outcome is minimal. Might as well base your retirement planning on winning the big lotto and those odds.
3: Even it did make a difference, in the grand scheme of things it makes minimal difference in who get elected, unless you are one of those robotic ideologues or perhaps a one issue types who think the world revolves around you and your issue. [Gotta vote to get your bribe]
4: Even if your vote made a difference, and the person who got in is significantly different, who is to say that it was actually the better choice. With the ignorance shown by the vast majority of people on all political issues, the odds that they will actually make an optimal choice is minimal. Even those 10% who are informed, you can easily be smart and knowledgeable yet wrong.
Also
When you vote you provide legitimacy to the system. To the corruption. To a political system that is designed around buying peoples votes by giving them the delusion that there is a disconnect between taxes and services. "I like this program because it benifits ME!, and if it is bad for the rest of the country, or morally questionable, then fuck 'em, I gets mine", no thanks, I will not take part. If you spoil the ballot, it is understood that you are just too stunned to vote properly. It is only when turnouts drop that people start the question.
But hey, if you want your pork, you might as well take part in the process.
It is much like voting between a turd sandwich and a giant douche. Why bother.
Voting is like wrestling with a pig, you get covered in filth and the pig enjoys it.
No doubt your typical voter and political activist will not grasp what I am saying, so allow me to translate in terms you may understand. Oink oink oink. Oink oink oink.
Unless the rhino party runs, don't vote.