It’s a very bold assumption that graduating from undergrad means you are intelligent.
Any ‘80s high school flick will point out the gaping rift between the “hip and cool” and people with brains.
The Army has historically maintained a Bachelor's degree as a commisioning requirement. Certainly, there are people (i.e. OCS) who get commissioned without one, but once commissioned they get a set amount of time to complete it. I don't think any level of intelligence is assumed, but the paper is used as a general indicator of motivation and some ability to learn new information and apply it.
The Raleigh/Cary area has the largest percentage of PhD’s in the world!