Many software and equipment are installed with default configurations and passwords.
Very often, these passwords are not changed..

Vendor          Username      Password
------          --------      --------
Raspberrypi     pi            raspberry
3COM            BLANK         12345
APACHE          admin         jboss4
Apache          admin         tomcat
Apache          tomcat        tomcat
Adobe           admin         admin
Airlink         BLANK         admin
Apple           admin         public
Belkin          admin         none
Borland         politically   correct
Bunker OS       BLANK         123456
Cisco           EAdmin        BLANK
Cisco           BLANK         Cisco
D-Link          BLANK         private
Del             Administrator storageserver
Edimax          admin         123
F5              admin         admin
kali            kali          kali 
Netgear         BLANK         password
parrot          user          toor 
Raspberrypi     pi            raspberry
ubuntu          user          BLANK