The only time I ever expelled a live Tapeworm segment (or any moving parasite) was when I consumed a raw paleo diet inspired by Aajonus Vonderplanitz and Vinny Pinto. It occurred with usage of MH's dewormer product. It also caused crawling around my body which dissipated after a few days.
I never expelled any live parasites while eating a healthy vegetarian or vegan diet. Only dead parasites in conjunction with Liver Flushing and parasite cleansing. The flukes were left over from years of liver debilitation starting in early youth on the SAD.
I do not believe parasites are inevitable. They are naturally expelled before development in a healthy human body.
Some people have treated illness with parasites. As far as I have heard/read, it has always been autoimmune disorders that are treated. The presumed method of action is suppression of the autoimmune response due to increased demand for immune cells in fighting parasites. It sounds exactly like what modern medicine is typically derided for, suppression of symptoms.