That's a loaded question! As though the Servlet API were some sort of malefactor, intentionally and improperly inhibiting the powers of righteousness!
Let's calm down, people. Remember that Servlets have been with us for over a decade, so no one knew when the notion of a Servlet was fleshed out what we'd want to do with them now. So for example, the fact that the Servlet API assumes one thread per request is now essentially an obsolete notion. There's nothing "improper" going on -- more a case of new tools solving new problems where old tools cannot.
This was first published in July 2008