On Expectorating and Perspiration

I do not understand the need to expectorate one's nasty saliva in an open, public place. Does a person's mouth become so disgusting that they are unable to swallow, or the buildup of saliva begins to cause an overflow, therefore requiring them to spit? I personally do not appreciate the need to dodge spit-globs while walking about. Let's keep our bodily fluids to ourselves, shall we?
While on the topic of bodily fluids...
I understand that perspiration is a natural fact of life. It is a necessary bodily function. It also, however, often causes discomfort or embarrassment. This is why I sympathize with my professor. As he discussed philosophy in class, raising his arm and resting his hand on his head, he was unaware of the giant pit-stain soiling his shirt beneath his arm. Poor man. He seemed oblivious. It is difficult for a classroom of students to exert their full attention on the lecture of a man shoving the salty fluids excreted by his pores in their faces. When are deodorant companies going to consider the educational damaging affects of perspiration and do something about it? He is an intelligent man, his image tarnish by his sweaty pits. sad