I come at it from a pure FICTION FIRST perspective. In the case of combat, if there's a fictional situation which allows for an attack, then the player can fictionally describe his character's intent to make an attack, and the GM is then OBLIGED to process this in accordance with the combat system rules. She doesn't really have a choice, though in 5e maybe technically she could say 'no' I doubt that would fly. Likewise, if FICTIONALLY the PC is in a position where Intimidating some NPC is possible, then the GM in good faith has to invoke the intimidation rules.
Since we are talking about 5e we have to have a reasonable chance of success, the outcome has to be uncertain, and failure has to be interesting before a (non-combat) check should be called. Frankly, if I ran 5e, I would take this as basically "Say yes or roll dice." If failure isn't interesting and the action is fictionally possible, then the character succeeds! Even if the outcome is not, logically, certain, failure is uninteresting, so we assume it doesn't happen and go on. This is a game after all.