As everyone knew, Hogwarts was the safest place in the entire world.
Never mind whether anyone else acknowledged it; at any rate, the wizards of Great Britain's magical world—especially loyal fans of Professor Dumbledore represented by Hagrid—all believed so.
And judging purely from the numbers on paper, Hogwarts really was exceptionally safe.
It had Dumbledore, the world's most powerful wizard, serving as Headmaster and guarding it personally; Fawkes, one of only two Phoenixes in the world that followed wizards, acting as a highly mobile vanguard; and the Heads of the four Houses, professors whose combat strength ranked among the very best in the wizarding world...
Never mind whether it was a fake galactic battleship—just tell me, was that lineup strong or not?
With such powerful wizards guarding it, Hogwarts being the safest place in the world was only perfectly reasonable.
As for Hogwarts frequently "wearing out" Defense Against the Dark Arts professors, the Philosopher's Stone being stolen by a Dark wizard's invasion in '91, the Basilisk running rampant in '92, Dementors crowding outside in '93, and the string of dangerous incidents during the Six-Wizard Tournament in '94...
Accidents. They were all accidents! Please do not let a vast number of isolated cases affect your opinion of Hogwarts!
Whether you admitted it or not, Hogwarts remained the safest place in the world—just as safe as North American Muggles' Area 13.
And in order to maintain its title as the safest place in the world, Professor Dumbledore could only work a little harder—
Professor Dumbledore had always had a good habit: every so often, he used the Headmaster's authority to inspect Hogwarts Castle, thereby ensuring the school's safety.
And during every inspection, Professor Dumbledore detected magical traces of the curse Voldemort had once placed upon the Defense Against the Dark Arts course.