We use AC because changing voltage levels with it is extremely simple and efficient compared to DC.
In fact the only (practical) way to convert DC voltage levels is to convert to AC, do the level conversion, then convert back to DC.
Believe it or not, DC already is more efficient for energy transfer and why there are already DC high voltage transmission lines. You don't have to deal with reactive parasitics.
But again the killer is that AC voltages are so easy to switch and can by done with >99% efficiency.
In fact the only (practical) way to convert DC voltage levels is to convert to AC, do the level conversion, then convert back to DC.
Believe it or not, DC already is more efficient for energy transfer and why there are already DC high voltage transmission lines. You don't have to deal with reactive parasitics.
But again the killer is that AC voltages are so easy to switch and can by done with >99% efficiency.