Why do all animals look each other in the eyes?

sure they pay attention to peripheral vision and will glance at parts of you when judging stuff. arthopods, i think, are looking at our chest like a segmented thorax with arms. but all vertebrates and mollusks seem to. is it that microemotions have always existed with the eyes and evolution made a wide variety of organisms able to read bluffs and intents of prey/predator/competition/mating behavior.