Why does everyone put celery in soup stock?

It's winter so I find myself eating more soups and stews. They can be so good on a cold day.

But IMO celery tastes horrible and only subtracts from the flavor of soup by covering up other flavors. Why is it such a common ingredient? Do people actually like enjoy or is it serving some other purpose?

(Yes I avoid it in other foods too. Not to go off topic but water chestnuts are a fantastic substitute if you like the crunch. Try them instead of celery next time you make stuffing.)