The point of attending a University is that at the end of it, the University confers upon you a degree that asserts your knowledge in the relevant field of study. That degree is valid forever; the University doesn't later get to take it back if you're actually a buffoon. You receive the credential, it has value, and its conferral is guaranteed as long as you complete the requirements of the degree.
By contrast, interviews are extremely condensed and an interview doesn't guarantee you a job in the same way that completing degree requirements guarantees a degree. Employers also have the option of firing you later.
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The point of attending a University is that at the end of it, the University confers upon you a degree that asserts your knowledge in the relevant field of study. That degree is valid forever; the University doesn't later get to take it back if you're actually a buffoon. You receive the credential, it has value, and its conferral is guaranteed as long as you complete the requirements of the degree.
By contrast, interviews are extremely condensed and an interview doesn't guarantee you a job in the same way that completing degree requirements guarantees a degree. Employers also have the option of firing you later.