The cgi model(also inetd) starts a new process on every single request.

If you wrote your service in C like god intended(sarcasm) this is not a problem, unix systems are traditionally by design very good at starting processes.

However python(my favorite language for what it's worth) has a lot of baggage it needs to sort out when it starts. so python specifically and any interpreted language that takes more than a few milliseconds to start in general starts to suffer under heavy loads in the one process per request model.

Thus the motivation to make it one process for many requests.