Why did Frank Lloyd Wright use wide low roofs and continuous bands of windows in Prairie houses?

Frank Lloyd Wright utilized wide, low roofs and continuous bands of windows in his Prairie style houses to move away from the conventional, boxlike structures common at the time.1

These design elements served several purposes:

• Defying Convention: By incorporating continuous window bands that turned corners and broad, low-slung roofs, Wright broke the rigid, compartmentalized nature of traditional residential architecture.1
• Spatial Flow: These features helped create an environment where the main rooms of the house flowed together into an uninterrupted, spacious living area.1
• Modern Integration: The use of broad, glazed areas allowed for the integration of modern building techniques, such as perimeter heating, which was placed below these windows to ensure comfort and convenience.1

Ultimately, these design choices were part of Wright's broader vision to create a new, appropriate Midwestern architecture that emphasized spaciousness and a radical approach to modern home design.1