It's not "Harley Guys" getting away with anything. HD, Triumph, Guzzi, and all the Japanese manufacturers factory equip cruisers with 2 auxiliary lamps to compliment the single headlight.
Electraglide, California Vintage, etc.
55w is legal in the USA for AUX lights. Some people run 35w, but that is thier choice, not the law.
The size doesn't have anything to do with anything.
Where did you come up with this stuff ??? Seriously ???