Picture air taking the shape of your tube as water would take the shape of a glass. 1 it isn't really sucking in air until it hits the air filter, it is just drawing in air from the location. So with that being said the air that is getting caught in that hose is filling out those indentations, so if you had a drop in pressure during shifts and what not, the hose would continuosly contract and expand because of that play and flexibility in the hose. Whereas hard piping, smooth and solid would not have that problem.