Profits over everthing, if you make food that's horrible for the body it tends to have an insane shelf life. Ultra-processed food can be on the shelf for ages before it needs to be tossed. Due to this, it increases the likelihood someone will by it, and the share holders only care about sales! Plus, the FDA is paid off by these companies so they can pretty much make carcinogenic food that last forever without any repercussions.