It has always seemed a bit strange to me that the console ports on networking gear are 8P8C (popularly referred to as "RJ45" even though that's not strictly applicable here) connectors and require an adapter to connect to a DE9 serial port. What is the reason for this? Is it entirely to make better use of panel real estate?
Out Of Band management is the only thing I can think of. A specific port that gets you into the device that doesn't rely on the communications-plane being managed. In the beginning, all comms techs HAD serial laying about, and it was easy: just plug the port into your serial terminal and configure. No mucking about with Ethernet, DHCP, BootP, or RARP, or figuring out what IP the switch auto-configures for itself.
And then inertia happened.