Because the Klingons didn't change... they got a cosmetic upgrade.
But even they explained something as small as that.
What? No. The Klingons got a *massive* overhaul to their lore, personalities and culture. They were originally just a simple cold war stereotype. By the end of the 80s they had a fully developed language for pete's sake.
But we're off topic now...
It's not that I'm unsympathetic to your position. There are certain IPs Im very protective of. Just suggesting that this might not be as important as your initial reaction leads you to believe.