What do you think Thornton Wilder's purpose is in using no scenery or props in the play?

It is an unconventional work in that it has no scenery or props except for tables, chairs, ladders, and a few other objects. When actors dine, they hold imaginary utensils and eat imaginary food. When looking out an upper-story window, they stand on ladders. When the milkman makes deliveries from his horse-drawn cart, there is no horse or cart, although the audience may hear clip-clops or whinnies. And so goes the entire play. Author Thornton Wilder presented the play in this way to force the audience to concentrate on the characters and the themes and not the setting.