Because doing that is an invite to the field of weak/conflicting evidence because food science just don't have this level of granularity yet. Though I believe to be undeniably that the replacement of ultra-processed cheap foods with real food is beneficial. I'm too lazy to research it for the sake of an argument but I can support it at least on a personal/anecdotal level. It's not scientific but as a rule of thumb if you don't know how it was made better to not eat it.