[Discuss] Separate commercial firewall?

[John Hall]

In what cases is an integrated firewall in a good home router insufficient?
If it's not necessary could this unit actually compromise security?

When I was visiting my folks for the holidays I noticed that their media
equipment company installed a separate hardware firewall between the cable
modem and wifi router.  i don't remember the make but I recognized it as
high end. It's not a standard consumer brand and was about the same size as
their wifi equipment. They really don't know it's there let alone use any
active features like detailed logging.
Being very generous the network is used at peak by 8 people.

At first I figured that it probably was a way to just charge more money but
have started to think...maybe their are vulnerabilities I don't know about.