Residential and commercial buildings are different; different topographical plan, different conditions and different painting. Time for businesses is money, so any delay during a painting project can increase the cost for a business. That’s why proper scheduling is important.
Then you have the scale of the project. Residential buildings are small and not that complex and can be done by one or two professional painters. Also, the amount of paint that is required is far less. Depending on commercial activities, quality and type of paint is important too (e.g., dusty environment or high humidity etc.)