Why only have black color, white color, or metal brush for the robot vacuum?

Why only have black color, white color, or metal brush for the robot vacuum? Let's have some personality to our home appliances.

YH-212 : https://www.yht.com.tw/en/product/film/Light-Cement-Stone-YH-212.html

YH-283A : https://www.yht.com.tw/en/product/film/Black-Marble-YH-283A.html