briter: "one of the main reasons it is compulsory is because of...

briter: "one of the main reasons it is compulsory is because of the $2.00 they get for each primary vote."

Not only pessimism but cynicism.

The word is a compound of "demos" which means the people and "cracy" (or kratos) which means power, strength, etc.
Democracy is a system that shows that the people -not dictators- run the country. The people can only run it if they express their views on everything that affects their country. There will be no "power" if it would be allowed that some of the people vote and others don't. There'd be no mandate, no authority and no legitimacy in the rulling party if it can't claim that of the whole population who voted, they were in the majority. They were preferred from the others by a majority of the whole population.
Abstaining is not a part of the Democratic system. The ancient Greeks were given two pebbles with which to vote: one black and one white and that's how they voted, Yeae with the white and Nae with the black. There was no "abstain" pebble.
How do we greet people who call themselves "leaders" of an organisation or a country who've been elected by the majority of only those who were simply able to elect or bothered to elect? Surely their legitimacy would be questioned.
A govern't is forced to provide access to the remotest in the community, to those of its members who are overseas, to the sick and the disabled so that a full count can be made -and accepted by all- of the majority opinion of the constituent parts of their society or organisation.
Here, in Oz, we have an absolutely delightful system of preferential voting. You can vote in such a way as to give a bit of a lesson even to those who you'd rather prefer to be in Govn't. That bit is great.
But we could also learn from the Yanks (who, in fact, practice little democracy as such) in that they have fixed terms of leadership. It help, a little only, I know, with overbearing corruption. That's why we're the mess we're in, here.