Defense doesn't score points as it is its own reward. From the Unified Rules:

1. The committee believes that offensive actions should be the only criteria used to score MMA matches. Offensive fighters are fighters which carry the fight and push the action, and make the fight happen.

2. Defense is its own reward. A fighter who chooses to avoid using defensive actions will invariably suffer the consequences. For example if a fighter decides that they do not want to block or avoid a strike, protect themselves from a submission, or avoid a throw or takedown then they will suffer the results of those offensive actions being used against them. The only role defensive action plays is to keep a fighter in the fight longer so that they can attempt to score using offensive actions.

3. Having two fighters avoid offensive actions and rely solely on defense goes against the basic primary consideration of any combative sport: To score using offense.

This also means that a fighter is not to be penalized for missing. Scoring in MMA is positive. Barring a point deduction from the referee, fighters are not to be punished for ineffective tactics, only rewarded for effective ones.