I think two factors are in play:
The first is that there is likely more diversity the deeper you go down the intellectual hole. You and I may read much more sophisticated books, but the books you read and the ones I read differ significantly. Thus, the list is biased towards the more popular (it is, after all, a popularity list).
Second is this:
> for engineers to be detached of liberal arts?
Most of us just haven't found value in the other types of books. It would help if you gave some examples of books that should be here. For me (perhaps as an engineer), I like books to kind of get to the point. When it comes to fiction, I'm a very firm believer that, although a given novel may give great commentary about a social/philosophical issue, its primary purpose is entertainment. If I wanted to understand the underlying social/philosophical issue, a more direct, nonfiction book will always do a better job.
I've yet to find someone "changed" because of fiction. Those I know who claim to already had the sentiments before they read that piece of fiction, and the story was merely preaching to the choir. What they are glorifying is how well the story depicted an issue.