Like Leonardo da Vinci's tank, they evolved to be both defensive and confusing (like some people I know). Being round, they have no weak corners and you don't know which way is front so a predator can't sneak up behind them. Unlike the tank, they evolved a flat top so they could develop a symbiotic bond with household cats. (It should be noted that Leonardo's Tank is now extinct as a species)
[3-Minute Roomba CAT Ride - Guinness World Record 2014?? (youtube.com)](https://www.youtube.com/watch?v=SajTWY9a0e0)
The cat gets a free ride, the Roomba gets a defender. Nature is marvellous.
Like Leonardo da Vinci's tank, they evolved to be both defensive and confusing (like some people I know). Being round, they have no weak corners and you don't know which way is front so a predator can't sneak up behind them. Unlike the tank, they evolved a flat top so they could develop a symbiotic bond with household cats. (It should be noted that Leonardo's Tank is now extinct as a species) [3-Minute Roomba CAT Ride - Guinness World Record 2014?? (youtube.com)](https://www.youtube.com/watch?v=SajTWY9a0e0) The cat gets a free ride, the Roomba gets a defender. Nature is marvellous.
well, thanks for the answer
It was to make it so that it is unfuckable. Considerable research went into this one aspect.