> My understanding is that 3.0 ports are backwards compatible with 2.0 devices, and automatically default to 2.0 levels of power when paired with them.

Not perfect compatibility though. E.g. some older network cards, installers for older operating systems, specialized hardware etc. might not work properly with the 3.0 port but will work in the 2.0 port:

https://superuser.com/questions/1112714/why-do-modern-computer-cases-still-have-usb-2-0-ports

That is particularly relevant for "work", where you might have specialized, old and very expensive equipment, hence many "business notebooks" did leave one port as usb 2.0.