Why do you think most models show the scale sizes of the planets but do not show the scale distances between the planets?

If both distance and size are proportional to that in the solar system, the model would be essentially useless.

For example, if the sun were represented by a marble 1 cm in diameter, the planet Neptune would be represented by a grain of sand. 3 mm in diameter about 32.3 meters (106 ft) away. The largest planet, Jupiter, would be a larger sand grain, 1 mm in diameter, about 5.6 meters from the sun. Earth would be less than 0.1 mm in diameter, about 1 meter away from the sun.

Such a model would barely fit into a gymnasium (basketball court), and the elements of it would be very difficult to find without a map.