This might be obvious, but you can charge your Pocket by running a USB-C cable from your charged iPhone, iPad or Mac to your Pocket device. This could obviously be handy if you need a top-up. Importantly, Pocket continues normal operation while charging.
While many charging questions focus on magsafe charging, which could be useful (but really only in situations where you’re not actively using Pocket), universal USB-C charging is far more useful in real-life situations 
This alone could be reason not to get the closest competition to Pocket which uses a proprietary charging cable.