What are ways I can convince my bf that there are better outlets than weed ?

I know a lot of people find it not a big deal but I really hate that he does it. It used to be “oh only sometimes” to “only on weekends” to “oh when I hang with friends so some week days” to everyday even when I’m with him. I can’t take it but I really like him and that’s the only problem I have with him and idk how to fix it.