The more meat you eat, THE SOONER YOU DIE.
The more meat you eat, THE MORE MAJOR DISEASES YOU EXPERIENCE BEFORE YOU DIE.
The more meat you eat, THE MORE OF OUR COMMUNAL ENVIRONMENT IS DESTROYED.

You really have to be sticking your head in the ground to ask, “why not?” Like literal psychological denialism. Just look: https://duckduckgo.com/?q=meat+“all+cause+mortality”