I'll second the reasoning that it's probably out of habit mainly.
You'd need to educate users to look for 240V bulbs as replacements, but at least the "funny looking" BC bases would stop them just screwing in regular 120V ES bulb and the resulting consequences. People these days are probably more used to looking for unusual style bulbs anyway with the varieties commonly used in microwave ovens.
By the way, Whirlpool now manufacture washers and dryers for the British/European market. I was in Comet (big electrical retail chain) a few days ago and saw the large Whirlpool machines (take about a 22 lb. load) on display, complete with "Made in U.S.A." tag on the panel, so at least some production in the U.S. is already for 240V. If they can turn out export machines for 220-240V 50Hz, then it probably wouldn't take too much to do a 240V 60Hz range to UL/CSA specs.
(Nice to see American-made appliances on sale here, by the way. They're few and far between on the whole.