In PRCustom : why cant we make use of existing servlets : PRWebLDAP1, PRWebLDAP2, PRWebLDAP3

Pega OOTB provides three servlets in the web.xml as below :

Servlet Name       AuthenticationService   App URL

PRWebLDAP1     AuthService1                 http://hostname:portno/prweb/PRWebLDAP1   
PRWebLDAP2     AuthService2                 http://hostname:portno/prweb/PRWebLDAP2
PRWebLDAP3     AuthService3                 http://hostname:portno/prweb/PRWebLDAP3

• Servletname would goto URL of the application as specified in column 3 of above table. 
• We would need to have a desired name w.r.t the application specific URL, so we create our own servlet mapping. Example : http://hostname:portno/prweb/ClientCustomAuth
• In this example, we need to create a new Authentication Service rule, and map this AuthService rule to ClientCustomAuth Servlet present in web.xml