Why does every recipe on-line call for beef broth?
Well, because store-bought beef broth is infinitely easier than making your own. Unfortunately, the vast majority of recipes you'll come across (online or in books) are designed to be convenient and simple in order to gain the author exposure with a wider audience.
There are, however, many good recipes for homemade beef broth and I encourage you to try it out. Just replace the store bought broth in the recipe with the one you've made. I would also encourage you to use recipes you find online as just a guideline. For something as "simple" as a beef vegetable soup, one should listen more to their personal tastes than a recipe.
Broth with browned beef bones = stock ( https://www.youtube.com... ). So I am assuming that your grandma and aunt skipped making the stock separately (with normally people buy from supermarket) and just directly make the stock and the vegetable soup in one go.
I think that these recipes are just shortcuts. Real soup calls for browned beef bones. BTW you can brown veggies too, it gets even better.
Finding bones for broth is getting to be a problem and expensive around here. If your OCD don't read any more. But save leftover bones from eating ribs and steak in the freezer for making a broth.