Typically, the United States democratic system is designed to allow competent presidential candidates to run for the presidency of the United States. However, when the system fails, if voters are unhappy with their choices currently their only course of action is to not vote. This means they don't have a voice.
Adding the NOTA option, which exists in other countries, would allow people to express their displeasure with the current system by selecting "None of the Above". In the instance that "None of the Above" receives the majority of votes, then reevaluation and recampaigning for presidency would be required.
The NOTA option is a fundamental necessity to maintain democracy. Adding it to the ballot gives everyone a voice and ensures true democracy is not compromised.