That gets us into the history of Servlets - the first API, servers and books made extensive use of the /servlet/ convention.
However, as the API evolved, Sun wanted to make servlet/JSP applications (and
J2EE applications) very standardized, easily "plugged in" to servers, and transparent (not obviously servlets). Not using the /servlet/ convention helps with all three.
Starting with Tomcat 4 (as I recall) the invoker was no longer on by default in order to help this transition.
Bil