There is an entry at the oxford dictionary that begins with
The popular image of student life is of young people with few responsibilities enjoying themselves and doing very little work
Why didn't it say
- "of the student life"?
- "a student life"?
The popular image of student life ...
The noun life does not refer to a specific instance of life, but rather life in general.
Keep in mind that life here is actually part of a prepositional phrase which combined serves to qualify image. The sentence talks about an instance of an image and therefore that has an article.
In this case student is a noun adjunct modifying "life", to elaborate on what kind of life is being talked about. Without it, it becomes
The popular image of life is of...
which sounds fine. It wouldn't sound right if you added articles, because then without the noun adjunct you'd either be saying
The popular image of the life is of...
The popular image of a life is of...
which both sound off because you're talking about life in general; you don't mean an individual person's life, so articles aren't used.