If you're talking about jobs, most humans have a plethora of survival options.

Once a wild animal is trained to an easy single source of food, it prevents them from naturally diversifying their diet to prevent starvation, removing that natural challenge could be deadly.

This isn't just about doing a task and getting a reward, this is about addiction.

This experiment would not be removing any existing food sources but adding another one. I doubt there will be enough cigarette buds for every single crow for it to become the dominant method of obtaining food for the whole species.