Dubbo 默认线程池的线程数量为200，这样有什么作用？

Question

<!-- 配置时未指定线程相关配置 -->
<dubbo:protocol name="dubbo" port="${dubbo.port}" />
<!-- 则等同于以下配置 -->
<dubbo:protocol name="dubbo" dispatcher="all" threadpool="fixed" threads="200" />

附上线程池源码

public class FixedThreadPool implements ThreadPool {

    public Executor getExecutor(URL url) {
        String name = url.getParameter(Constants.THREAD_NAME_KEY, Constants.DEFAULT_THREAD_NAME);
        int threads = url.getParameter(Constants.THREADS_KEY, Constants.DEFAULT_THREADS);
        int queues = url.getParameter(Constants.QUEUES_KEY, Constants.DEFAULT_QUEUES);
        return new ThreadPoolExecutor(threads, threads, 0, TimeUnit.MILLISECONDS,
                queues == 0 ? new SynchronousQueue<Runnable>() :
                        (queues < 0 ? new LinkedBlockingQueue<Runnable>()
                                : new LinkedBlockingQueue<Runnable>(queues)),
                new NamedThreadFactory(name, true), new AbortPolicyWithReport(name, url));
    }

}

这样默认会启用 200 个线程，按照正常对线程池分配线程数的逻辑，不应该配置这么多啊。我想知道为什么默认要设置为200