If that's the case, then why bother to refrigerate anything you're going to cook? Why did people put it in salt (which kills bacteria in the olden days?

The reason is that microorganisms leave behind toxins that don't cook away.

Yes, and cooking also aids digestion and taste. But not all (in fact only a few) microorganisms are bad for you.

Most of the time bacon is already smoked or cured anyway.