Becase some devices require a signal on their comm pins to negotiate the correct voltage to charge the device. Also some devices are dicks and needs a proprietary signal in order for it to charge. Looking at you sony.
Sony and proprietary nonsense, name a more iconic duo
Apple, Samsung, all the Chinese phone brands with their proprietary fast charging standards, HP, Bambu Lab, Nintendo, Xbox, Microsoft, Google, Adobe, etc. etc.
There’s a lot of terrible companies, actually.
Nintendo and it’s propriety hardware
Apple?
The hub doesn’t have a negotiation chip to set the voltage correctly. It is likely presenting as a bus hub. Like if you do
$ lsusbon Linux, you’ll see the hub and whatever is connected. That hub may be integrated into other chips or it may be stand alone as a peripheral somewhere on the board. It is basically like a digital cable splitter for the bus. It is only concerned with the data. The power is likely just passed through. For USB-C PD, it would need some complex additional circuitry to negotiate, convert voltages and do current limiting. The way the pins can be inverted by flipping the connector makes it logically complicated.Speaking of passing through PD communications, I have a cheap Chinese power meter that sort of does that but not properly. Hopefully, OP has a good hub that plays nice.
If you use a setup with a power supply, first cable, power meter, and a second cable, you can measure things when connected to a chargeable device like a laptop. It obviously tells the PS to give it 12 V, which it will. Once you unplug the laptop from the second cable, the voltage reading doesn’t drop back to 5 V. Apparently, the power meter doesn’t let the PS know there’s no load anymore.
As a result, you get a USB-C cable that gives you 12 V without asking any questions. Guess what happens when you plug in something that can only handle 5 V? Bad things. Don’t ask me how I know.
Anyway, once you unplug the power meter from the first cable, the PS finally gets the message and drops the voltage back to 5 V. Makes me wonder if a hub could behave the same way as my power meter.
I’m guessing the driver on the PC regulates the power somehow and not any logic on the hub itself.
