Everything is Marketing, it is what you convince your audience of, not whether you have it, know it, or can do it; and it is not your confidence, it is the decision maker's confidence that you can do it that wins every time. Everybody needs an elevator speech. And the speech needs to be practiced and refined so that it can be delivered and executed flawlessly at a moments notice. Depth, in experience, knowledge or skills, is not the relevant factor, presentation is.
Tied to this is the ability to get someone talking, talking about themselves, their problems, their wants. This extends any conversation, puts you in an empathetic light, and gives you information to adapt, at least focus, your pitch of selling yourself. If you can put yourself in a picture or vision of unburdening their problems or delivering their wants, getting them to that association of you and that positive outcome. That association is needed because they won't be thinking of you, it's those other things that keep them up at night, the association you make is laying that bridge that takes them to you, makes them even consider you.
The spontaneity of this is needed as success is seizing an opportunity, very few people have the outright tenacity let alone influence and power to just plan to do something and then just do it. Best selling authors, top level executives, political leaders all seized opportunities that were presented to them, not that they made their own opportunities. It was being in the right place at the right time, not to say they didn't work hard to get there or stay there once they reached it, but they had to sell themselves, convince someone to take a chance on them, market a decision maker to decide on their behalf.
And everyone is subject to a decision maker somewhere. Some get to also be decision maker for some number of others. No one is immune from needing this skill to be successful, in any market, any career, any situation.