If really we want to go with what is technologically accepted, one shouldn't charge his/her phone device with other than a stable electric power supply. But as it seems, it doesn't really work this way, perhaps due to poor power supply in some parts of the world. And the effects of this development of charging phones with alternative power supply are bad on the battery life of these devices.
However, phone batteries are designed with materials that are sensitive to the stability of the kind of power used in charging them. Unfortunately, so many people are no aware of this fact, that's why they can go ahead and charge their phone with unstable power source.
Looking the issue holistically, they are not the ones to be blamed, because they only find themselves in situations they are helpless of, as they are faced with challenges of unreliable power supply, which leave them with no other choice than to make use of what is available.