Comment 1 for bug 1727313

Tools that try to simplify for the user like virt-manager already define a whole array of usb controllers (that is one of the effects when you select the Guest OS to be a modern Linux).

Libvirt as core helper has to rely on the lowest denominator unless otherwise instructed.

This bug was mostly for documentation, I think it would be wrong to change the default and break older guests. So closing as opinion, but now available for others to find - and the suggestion to add such a controller might help a few people.