Why use a container?

[Mark Slater]

I get the feeling that I'm missing some simple, yet vital, part of the 
Web Services / SOAP implementation. Essentially, I'm trying to 
understand why an app container (like Tomcat) is a Good Thing for a 
SOAP based web service. What is it that the container provides that's 
so useful? As I'm writing my own small web services to learn more about 
the protocol, I've been writing them as simple CGI applications.

I guess, my (possibly skewed) perspective is that a web container adds 
another level of indirection, and since most of them seem to be written 
in Java, doesn't that slow things down more? I've been writing my 
programs in C++, but I understand that to do more complex programs I 
don't want to be parsing the XML myself, and that's where an outside 
SOAP library comes in handy, but even Axis C++ seems to need the Java 
interface.

So, to summarize, I'm trying to find the answers for these questions:
1.1) What is the rationale behind deploying SOAP-based services in an 
app container?
1.2) What does the container provide?

2.1) How does the performance of a container compare with "raw" CGI?
2.2) How would the performance compare to a CGI interface to an already 
running program that handles the requests (i.e. something that doesn't 
have to start and stop; the CGI program parses the SOAP and sends the 
request in some local inter-app communication format, and then bundles 
up the result and sends it back)? ... maybe that's what the app 
container is doing?

Thanks,

Mark