It's just retarded, there is no need to speculate or explain anything, the very concept is extremely stupid on a fundamental level. Should every person on earth who wants to use crypto in person also have a phone?
More people have phones than have desktop/laptop computers. It makes more sense to use phones than computers (by-the-way: you can easily adapt this system to use a desktop anyway).
Do you know how long the battery lasts for modern phones?
What does the battery charge life have to do with it? The coins don't disappear if the battery is completely drained. Neither do you have to continuously run the software. You only need run the software when doing an actual transfer and it uses a very small amount of energy.
In the future there will be small plastic computers the width of a paper bill that you would swipe against each other in order to pay, they will be so cheap to manufacture that you could simply swipe your reserves to a new bill instead of recharging, they would also be so efficient that you would be able to recharge them by manual means.
I don't even know how to reply to this? What are you talking about?