Many parasites infect multiple host species, with one host species being the definitive host (where the parasite reproduces), and the other host species being the intermediate host (where the parasite grows to maturity). (Further details described as "complex life cycle" at https://en.wikipedia.org/wiki/Parasitic_life_cycle ) Why is this complex life cycle so common? Why wouldn't more parasites adopt a simpler life cycle of just one host?
I knew that there were some parasites that infected more than one kind of host species, but now that I am looking into it, it seems like a majority of internal parasites have this kind of life cycle. Does anyone know why?