Hands up anyone who's actually had a wake turbulence incident in a lightie. They are a real eye opener (to use whatever the opposite of hyperbole is). Not everyone is lucky enough to have had one of those 500 hours in 20 second events, so a timely warning if you suspect someone isn't quite fully aware of the situation is hardly the worst transgression. And if you're wrong and you inadvertently bruise someone's mighty ego then that's probably not the worst thing either.