Well there's breadth of expertise. Part of CS is systems, which includes networking, operating systems, compilers, and so forth. If you're making any of those things or leaning heavily on them, you want to hire people who are grounded in those fields. Same goes for things like AI, machine learning, data mining, and so forth.
More generally, having seen more kinds of software kind of broadens one's way of approaching programming problems, so even if you don't directly use anything you see when you study operating systems or compilers or AI, you can grab vague approaches and ideas from those fields.
If you're interested in writing performant software, you'll care about big-O, algorithms, and data structures. Understanding algorithms and data structures enables you to intelligently choose and apply them even if you don't have to develop them from scratch.
More generally, having seen more kinds of software kind of broadens one's way of approaching programming problems, so even if you don't directly use anything you see when you study operating systems or compilers or AI, you can grab vague approaches and ideas from those fields.
If you're interested in writing performant software, you'll care about big-O, algorithms, and data structures. Understanding algorithms and data structures enables you to intelligently choose and apply them even if you don't have to develop them from scratch.