理论计算机科学的重要性在于它能够为实际应用提供基础。
The importance of theoretical computer science lies in its ability to provide a foundation for practical applications.
You can obsess about serving your customers/audience/clients， or you can obsess about beating the competition. Both work， but of the two， obsessing about your customers will take you further.
Every problem in NP can be reduced to the satisfiability problem, which is the cornerstone of computational complexity theory.