How do they discourage it? The staircases are very uninviting, they are narrow, and they are tucked away in obscure corners of the building. Take for instance the staircase I use for getting to the 5th floor, where my office is; it has grey PVC flooring, grey steel railings, and undecorated, white walls. It has few windows, and it is so narrow you can only pass someone with some difficulty. This is quite characteristic for the new buildings on campus.
The staircase in "my" building: not very attractive!
The staircase in the building that contains the labs
When this building was built, CO2 levels were maybe 80ppm lower than they are now, and who knows how much lower the average English BMI was. It was good to have these staircases back then, but we really need them now! If I ever enter the newest building on campus I'll search, with fear in my heart, for the staircases. I'll report back!