Not because it's hard to make interesting mustard -- you could make interesting mustard -- but people don't, because no one's obsessed with it, and thus no one tells their friends.
不是因为很难去生产有趣的芥末 ——你可以制造出有趣的芥末—— 但是没有人会对芥末着迷， 因此也没有人会把它告诉朋友。