From a friend of mine, in a chat thread about portable battery packs:
Fun fact: when we’ve had amputees test myoelectric limbs we’re developing, they often volunteer that they’d like a USB charging port so they can charge their phones from the big battery in the limb. We then explain that it’s a big engineering challenge to get the limb to last all day on a charge, as things are, so there’s not residual capacity for phone charging. They inevitably reply “If I have to choose between my arm working or my phone, I’m going to choose my phone.”