Because almost any authority can get it wrong. But since the authority is recognized as such, it can then perpetuate the error.
Case in point: The Oxford English Dictionary. It’s definition of “siphon” was penned in 1911. It was wrong then, and it’s been wrong since. Until now.
Of course, the problem is, many another dictionary has got it wrong, too, because they likely double-checked their own definition of siphon against the standard, the OED. And so the error rolled down the generations….
So the next time someone quotes an authoritative source to you, maybe an arched eyebrow is called for, instead of humble submission.
Sigh. How the mighty are fallen.
And an even scarier thought: maybe Wikipedia isn’t quite so awful, after all. 😉