My own addendum to the theory is that this is why they've introduced MagSafe charging – if you have a power bank in your bag that is supposed to be charging you

My own addendum to the theory is that this is why they've introduced MagSafe charging – if you have a power bank in your bag that is supposed to be charging your phone, but its wireless charging its just gonna fall off / come away from the charger. With magnetic attachment that is still more likely than an actual cable, but much less so.