Why do they need to be sweeping while open? Do you know dust raises while sweeping in front of open area where donuts are at

Because the floor is filthy and they want to stay presentable. Some people need to stay in a hermetically seal room. A little dust wont hurt anyone look outside it's called a desert.

Rather have the floor clean than filthy!!!

True, they do need to stay presentable. However there are opptune and more appropriate times for that.