Along that logic, what's the point of a dessert (or soup course)?
THAT did not answer the question. It just posed a new one.
I'm guessing you also find it odd that Italian cuisines often have a pasta course before the main course.
DITTO and that's a cultural offering, not really an appetizer. Italian meals are served in stages of different offerings as are French and probably other countries.
This staged dining also makes for an enjoyable evening of social dining with family and friends. Not eat your meal, get up and go on to other matters.
I've been trying to add new topics for discussion, not attack.
My feel on appetizers. First, I order them occasionally because I like to try different things. Sometimes a couple of appetizers are more attractive than one main meal. Other times I'm not as hungry and would prefer an appetizer sized offering.
I don't count soup or salad as an appetizer for some unknown reason. I won't always order a salad, but if the soup sounds interesting it's a given that I'll order it. It usually doesn't detract from the meal.
That said I think appetizers afford a diner a little taste of something besides their main meal. A little diversity in dining.
I also think that appetizers are money makers for the restaurant.... which is not a bad thing.