Imagine you’re building a car to spec. You can plan and design and draw and measure for weeks and months and build for more weeks and months.
And 3 seconds after you sit in it for the first time, you will know whether the location of the ignition and headlight switch is obvious. 3 minutes into your first drive, you will know whether the steering wheel is too far away, whether the pedals have too much travel, and whether the rear headrests obscure your view out the back. 3 days into your ownership, you will know whether your elbow will spill your coffee when shifting into 2nd, 4th, and 6th gear, and whether you can adjust the volume without looking.
Even the technicians building the car would not easily notice these things. The audio engineer might hold the finished audio unit in her hands, but she’d have to work to imagine what it would be like to use while driving. Another technician can manipulate the transmission a hundred times, and never even know there will be a cup-holder behind it. After all, the interior designer only met with him to discuss the material and labelling on the shift knob.
Everyone on the team, the customer, the head engineer, the designers, and all the technicians, should try to sit in the car, in all the seats, many times during the process. What they learn will improve the functioning of all the components and their integration.
And if the production is delayed? A customer who can come sit in the car anytime he wants, and see and feel the progress, however slow, will be happier than one who has to sit through another presentation of what the car will be like when it’s finished.