Consider how many people you affect when you go to the store to buy breakfast. You practically effect nearly everyone else on the planet by a very small value.

You're effectively choosing the administration under which people will live until the next election. This is a much larger effect than the marginal change to the economy from you buying breakfast.

I bet that higher voter turn out makes the result of the elections seem more legitimate to the populace emboldening the government for decisive action.

To through your other argument around back at you. What's the marginal effect of one person refusing to vote. Probably less than for one person voting since most people who don't vote do so out of laziness with no deeper philosophical motive behind it. Let's put it this way: a candidate with a majority (or even a plurality in some systems) becomes the office holder, whereas less than 50% turnout doesn't cause a revolution; and even if it did, it would probably not be the revolution you want.

Let's put it this way, the two reasons you've given for not voting are:

1) You're unlikely to affect the outcome anyway.

2) If enough people don't vote the government will have less legitimacy and this can have positive effects.

Since the logic of these two reasons contradict, would you mind telling me which is your true rejection?

If one desires small government the state having little legitimacy sounds like a good idea.

We still want the state to have enough legitimacy to secure property rights and enforce contracts.