You can't just buy anything you want with any kind of fund. Most of the time, you can't even buy the things you need for your research or for teaching because of some dumb regulations. Oh and when you buy something, it takes so long for the process to go through, that you might not need it anymore when you finally get it.
O is standing in front of a lecture hall
O: Welcome to the lecture “Creative Cross-Financing I”. This is a picture of the “business trip” that I financed using the funds of this lecture.
O is pointing at a picture of them on a surfboard
G and H are shown in silhouette, sitting in the audience
G: Will you also buy pizzas for everyone now?
G: Then I will tell the dean that you are wasting teaching funds.
O looks shocked and starts sweating
O: grumble Ok fine.
H: Wow, I already learned so much in this lecture!