At its core, theatre is not about telling stories.
The core of theatre is taking chances. Everyone involved in the process takes chances.
The playwright takes chances by telling a story that moves them, that is worth the investment of their time and the fruit of their personal creativity. The story needs to be dramatic (interesting) and truthful (reasonable and inevitable), true to the wide range of vagaries of human nature, understandable, logical, and (even in magical circumstances) wholly natural.
How does the playwright succeed in doing this?
By allowing the characters in the play to take chances to achieve their goals. This is why the play exists in the first place: to watch normal people in an overturned world dealing with (sometimes catastrophic) uncertainty. Were it only a normal day in the lives of these characters, no one would—or should—care. Drama is the opposite of normal. Drama should be the story that starts when mischance happens and the world of the play has a new situation that cannot (or can no longer) be ignored by those in the play’s world. A critical stress point has been reached, the status quo dam has been breached, the safe and solid world has been impeached, and this world now plunges headlong into a series of choices. Based on the choices they make — not knowing if they will succeed or fail, as they’re essentially groping in the dark for a light switch, sticking solidly with a moral principle, blind to everything except a personal obsession — some characters will achieve their desire, some will not. Sometimes they all lose, but that may be open to interpretation.
Given all this, the actors in the production take chances to find the emotion, timing, intentions, and truth of their characters. Each actor brings some different magic, some organic element, some peculiar and singular spice to a part. The best of them try different interpretations, sometimes even for individual lines or words, to keep it fresh, exciting, and new. It's not about “playing” the written character, it's about living that character and interpreting with complete honesty what's been delivered in the script. Are their dramatic choices good ones?
Directors take chances as well, with the vision of the play’s world. Does their perception honor the script’s intent? Is their staging (the emotional temperature, pacing, stage design, casting choices, etc.) faithful to the play’s mission?
Daunting considerations. Frightening, even, given the time spent in planning and rehearsal, the expenses incurred for what is typically little monetary gain, and eventual reactions of the paying public (and critics, if any deign to view the play).
And yet, thousands of normally harmless and intelligent people dedicate their creative time to taking these chances.
Living without risk is to risk not living.