I am busy. I am busy all the time. That is why, you the student who is not my PhD/MS student and has not been admitted to the program, has to take an appointment to meet me.
If you do not have an appointment (and I have a grant submission deadline) you will have to go back and get an appointment with me and then meet me. Otherwise I will turn you away (even if you traveled for 2 hours).
I am sorry. But my time is more important than your time and if you do not respect my time, I cannot respect yours.