I own a machine shop and a fair portion of the yearly income is from sharpening blades, from saws of all kinds, planers, metal cutting tools for lathes, band saw blades which I always suggest just buy the band saw blade in a 100 foot roll, cut and weld them together rather than sharpen the old blades.
Anyhow, I never had anyone come in and ask me to dull their blades. Sharper a blade, less torque and horsepower to slide the blades thru whatever you're cutting. You shall also use less fuel and the mower engine will run cooler during operations.
After I removed the paint from the blades, they still have a rounded "edge" of the blade. Its a about a 3/32" radius. Not acceptable.
Also, we were mower parts distributors for over 25 years. We would have returned the entire shipment to the manufacturer if we received blunt blades. Anyone tell you a blade is supposed to be blunt, rounded or have a shoulder on the "edge" of the blade and it will cut better. They'll purchase swamp land to build skyscrapers on it. lol Ok, bad joke.
Respectfully, cutting grass is no different than cutting lumber, metal or anything else. Sharp cuts, dull doesn't.