Power only USB devices do exist though I've never seen one in the wild.
I can't imagine they'd work with many modern devices which seem pretty fussy about dumb chargers.
e.g.
https://cpc.farnell.com/pro-signal/cdl-02power/lead-usb-a-male-a-female-0-2m/dp/CS23311?st=usb red
USB power mismatching and spec compliance is a problem esp. with USB C e.g.
Google engineer fries Pixel testing USB Type-C cable
I've also read of cheap USB chargers burning out because they negotiate with the device and try to deliver current they can't provide data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7I won't buy cheap chargers! That's definitely true and in some cases even vendor supplied cables can be poor so it's worthwhile buying some decent micro USB and USB-C cables.I think it's also handy to have a working card reader setup for a camera so you can be completely independent of the camera as card readers are usually quite reliable.
That technically isn't a USB compliant cable because one of the connectors isn't a USB standard although that said it does look like a cable can be power only by keeping all the required wires within the cable but not allowing any data.
I think that was the same guy who was showing how some USB-C cables weren't compliant and could damage devices which was alarming especially as the cables were from a company generally well regarded for their quality.It does highlight why this aspect of USB can be tricky to work with as it has to work perfectly otherwise there can be serious damage.
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