Why would we not include an end user’s PC device in a QoS trust boundary?

The end user could incorrectly tag their traffic to advertise their PC as a default gateway.

The end user could incorrectly tag their traffic to bypass firewalls.

There is no reason not to include an end user's PC device in a QoS trust boundary.

The end user may incorrectly tag their traffic to be prioritized over other network traffic.