It's McDonalds coffee, not cat poop coffee served by servants in tuxedos. I suspect purchasers of drive-through coffee would accept sub-par coffee at a temperature that doesn't cause severe burns.
Actually McDonald's has about the best fast-serve coffee available; this fact translates into very large profits from happy customers. That quality suffers fast if brewed under 195F and served under 180F; why opt for sub-par when being nigh unto ideal is easy? Some things that make life better are harmful if you do stupid things with them...don't put hot coffee between your legs.