A feature that's opt-in will get like 1% of the use of a feature that's opt-out. A happier middle ground would be to enable by default and show a "I don't like this, pls turn it off" button the first few times.
EDIT: shouldn't single out any specific role here. We think opt-out, enable-by-default makes a feature have far greater total utility. But we could do more to provide user agency for these features in-line during first use or find a different balance point.