Why has Apple not added fast charging on iOS devices?

According to the laws of thermodynamics, the faster electricity moves, the more heat it produces.

This is especially true in phones. The ones that support fast charging produce more heat. Where there’s heat, there there’s a metal layer to dissipate it. Where there’s a metal layer, there there is some amount of added thickness.

In an iPhone, adding thickness isn’t an option.
Adding a metal layer isn’t an option either.

Neither is adding wireless charging an option.