Democracy hinges on some essential elements which revolve around the decision-making process being reliant on all relevant persons having their say. Relative to a democratic country, it is the general public who must make informed decisions based on shared and transparent information. Political issues and specific agendas must be led by consensus and, in democracy, that consensus comes from acting in terms of a majority.
Effective participation and the opportunity to make informed decisions can only come from an enlightened general public and any interference, direct or indirect, can alter the essence of democracy. Intimidation is a universal problem across all types of government but, in a democracy, it can distort results and the outcome can be very undemocratic as there is a bias towards whomever initiated the intimidation.
Failing to vote in a democracy is an indirect form of interference as the consequences of inaction cause a bias, especially if it is people from a certain sector of society. Perhaps it is a marginalized group of people who are protesting against their status by not voting without realizing that they are actually contributing to it.
Democracy is intended to protect its citizens from oppressive and abusive governments. It also acts in the interests of most of the voters; hence, by not voting, citizens are excluding themselves from the democratic process, doing themselves, and democracy, a disservice. Compromise is a major element of democracy and issues which are within the voters' grasp escape the non-voter. Voters can hold their government accountable for the outcome of policy-decisions and feel confident that the decision will be based on a majority. However, non-voters must take responsibility for unfavorable decisions as, maybe if they had voted, there could have been a completely different outcome. Without voting, they are showing their support for a government or party that they actually would not ordinarily have supported.
Therefore not voting is not a way of protesting against a government or a structure. it does not weaken the opposition and it discourages competition between rival parties. It supports, perhaps unwittingly, bias and an undemocratic conclusion. Not voting actually threatens the whole democratic system.