These are not standard USB cables.
For the USB communication protocol to work it requires a host (and only one host). This is usually a computer, however most of the existing lightning cables expect the USB end to connect to a host. This would mean the iOS device appears as a 'USB device', like a hard drive on the computer.
In order for the iOS device to work as a host it requires 'OTG (On-the-go) functionality' and some electronics in the cable. This is usually done with a 'Camera Connection Kit', however these cables do it directly.
This allows things like audio and MIDI interfaces to be plugged in directly. Check your device to see if it's compatible with iOS as they must be 'class compliant'.
USB powering is usually provided by the host, so in this case it would either run from the iOS device, if it allows or just not work
Here's a bit more info on USB OTG functionality: