"Disgusting, it's just taking random kitchen items and eating them for the sake of eating."
Lordy, I know eating buttercream alone is rather polarising, but it's not the morally suspect binging on unrelated and random raw foods that people keep saying.
Although maybe you have something there, as although early prototypes of icing exist from the 1600s onwards, buttercream is a somewhat newer invention, coming into its own in the 1950s as rationing ended and people celebrated the influx of foods and ingredients to the high street, like butter, and icing sugar itself.
So with a history of merely 65 years I can see how it's still a newfangled and niche oddity :)
But with types of buttercream existing across different countries and local cuisines (such as Italy, France, Switzerland and the U.S.), it's not just an obscure Brit invention.
And buttercream icing is one of the most used icings in baking, especially on cupcakes, which are defined by the presence of the butter cream topping heaped on top. (And as cupcake sales are still measured in $billions in the U.S., and £millions in the UK, kinda big and mainstream!)
Anyway, that's a super long way of saying, buttercream is a type of icing!