I've come across some Windows administrators that are disabling Windows Firewall because "it makes troubleshooting more complicated".
The systems are protected by firewall appliances at the edge. They believe that is sufficient.
My question is: Assuming that the firewall hardware appliance is ideally configured, are there any concrete reasons to enable the OS-level software firewall?
Some type of points I am looking for:
Some information from an OS developer (Windows or non-Windows) with regards to the importance of the OS-level firewall
A demonstration or example of an exploit that is only possible if the OS-level firewall is disabled
Edit: Modified question after discussion in comments with @joeqwerty.