What's the advantage of thread pool in MySQL/MariaDB?

MariaDB thread pool

MySQL thread pool

I've read official document of MySQL/MariaDB thread pool,but I'm still confused about it; As I understand, thread pool has two advantages:

1. limit too many connections, too many connection could lead to too many context switches, but it seems option "--max-connections" also could limit connections~

2.reuse connected old thread:when a new connection is coming, unused old thread could be reused,but it seems option "--thread_cache_size" also could reuse old thread

so,what's the advantage of thread pool?