Setting a timeout is easy; setting the correct timeout is hard. If your timeout is too short, you drop valid requests. If it's too long, you hang resources and cascade failures across the system.
You gain the ability to use tools like Wireshark and TCPDUMP to inspect low-level traffic and find performance bottlenecks that high-level code analysis might miss.
Languages handle this differently. Node.js uses an Event Loop (Concurrency) while Java uses OS Threads (often Parallelism). Understanding your language's threading model determines whether your backend will scale or crash under "The C10k Problem" (handling 10,000 concurrent connections).