I think an important question to ask is: how much of a company's income comes from harmful use?

Gambling (and some other industries, in particular alcohol) come out so bad on this metric, you can practically let the industry define excessive use themselves. In order to claim most of their money comes from "healthy normal entertainment use" or similar, they'd have to claim absurd things, such as that drinking a bottle of whisky per day or spending your entire paycheck each month on slots can be healthy, normal use.