The round shape of many robot vacuum cleaners is primarily a practical design choice that enhances their efficiency and maneuverability. Several factors contribute to the preference for a circular form:

1. Improved Maneuverability: A round shape allows the robot vacuum to navigate more easily in tight spaces and around obstacles. The absence of corners or edges reduces the likelihood of getting stuck or wedged in corners.
2. Simplified Navigation Algorithms: Circular robots simplify the navigation algorithms that guide their movements. They can change directions easily, making it simpler to program efficient cleaning patterns.
3. Even Distribution of Weight: The round shape facilitates an even distribution of weight, which contributes to stability. This is especially important for preventing tipping or imbalance during operation.
4. Optimal Coverage: The circular design enables the robot vacuum to cover a wider area efficiently. It can rotate within its own footprint, reaching various corners and angles without requiring a complex chassis design.
5. Cost-Effective Manufacturing: The production of circular components is often more cost-effective than creating intricate shapes. This contributes to making robot vacuums more affordable for consumers.

While the round shape is common, it's worth noting that there are some robot vacuum models with D-shaped or other unique designs. These alternative shapes may have specific advantages, such as better corner cleaning. However, the round design remains popular for its simplicity, effectiveness, and cost efficiency.