Why no caps and gowns during commencement?

I just saw a clip of the commencement ceremony. Instead of caps and gowns, students dressed however they wanted, whether it was casual, dressy, or costumey. Why?

Given the choice, they chose not to wear cap and gowns

I understand they are given the choice, but I do not know why they are given the choice in the first place. I have never heard of a college that does that. Wearing a cap and gown at commencement seems like something that is always done.

NCF prides itself on eccentricity and individuality. It is also located in Florida, and can be oppressively hot in mid-May. Why do you feel that you, and not the college and its students, should get to make that call?