Some rules weaken, and others are created or subtly change - that's why parents can never get their kids' slang quite right. It's not that the parents can't simply weaken their grammar, it's that the kids do some things differently with very strict rules.
I know of a multi-million dollar company that was about to launch a new marketing campaign. We are talking ads, dozens of trucks getting rewrapped, marketing materials, catalogs featuring the tagline; the whole nine. It would have been tens of thousands of dollars spent.
They used "loose" instead of "lose" in the tag. The error was caught by the CEO's secretary without a degree.
It had gotten past upper management and the marketing department without being noticed.