There’s another big factor: soups and stews maximize the nutrients you get from your ingredients. If you fry a piece of meat you’re losing some fat, if you boil

There’s another big factor: soups and stews maximize the nutrients you get from your ingredients. If you fry a piece of meat you’re losing some fat, if you boil and drain veggies or meat you lose a lot. If you throw everything into a pot and stock/soup/broth is part of the meal, everything that went in goes into you. Soups and stews are also excellent ways to utilize preserved meats which need rehydrating, softening, and can make use of their salt content. Legumes and pulses pretty much require that treatment as well, and can thicken a stew or soup. Aside from equipment there is just the reality of nutrition.