I agree with all the people who are saying 'stop being so precious'.
It takes two seconds and no this isn't something people are used to.
A few years ago a P3 got caught in the wake of a C17 on final (I think Hawaii?) and required full aileron lock to maintain level. That's between two big aircraft with ATC services. A Cessna would probably be a hole in the ground.
I don't see it as dick waving. A lot of people genuinely don't consider that as they don't fly behind big aircraft regularly if it all. Not to mention a whole bunch of helicopters being in Medium/Heavy (Chinook by memory) that people are unaware of.
If operating a big aircraft and there's a chance a little guy behind me is potentially unaware and going to takeoff or land into it I'll say it. And I won't be upset if somebody reminds me when I'm flying little aircraft too. In fact I think next time I'll say thanks.