An empty deck can look spacious in a drawing. Furniture changes that quickly. Dining chairs need room to slide back, a grill needs a usable work area and the route from the door to the stairs should remain clear when people are seated. Accounting for those dimensions early can prevent a finished deck from feeling cramped.
The surface may need extra depth near a table while remaining narrower where people are only passing through. That kind of adjustment allows the deck to support its purpose without occupying ground that would be more useful elsewhere.
The rear doorway provides the starting point, though the yard determines where the design goes next. Stair placement can follow the route people already take toward the lawn or side gate. Cooking may stay close to the kitchen, leaving the farther portion of the deck available for seating without constant traffic moving through it.