I only speak for myself.
When I taught at a lower ranked state university, I could not make my class too difficult. I would lose too many of them.
Now I teach at a higher ranked state university, the quality of students is on average higher. More importantly, the tail is not that fat anymore. The same class is now designed to be more difficult. This is also exactly what most students want; they want to be reasonably challenged.
Note that I do not impose any curve. But my grade distributions have been quite the same for the Universities that I have served: about 15-20% A, 20-35% B, 20-35% C, 10% D and 10-15% F for required field core courses.