Observation from Almea: Maybe butter knives were invented by the butter industry. They're so dull that you end up taking more butter than you need (assuming the butter isn't soft), and you get a clump of butter that is very hard to spread on bread. For hard butter, sharp knives are far better, since you can slice thinly and spread the butter more evenly. But, this means no butter is wasted - hence, the conspiracy theory.