writes:

All maneuvers require training.

No maneuver (in the civilian world) when done in an aircraft certified for
the maneuver, performed by a pilot trained to do the maneuver, and done
under accepted conditions, is dangerous.

Why isn't spin training part of the PPL?

And before you ask, the accepted conditions are formed from the real
experience of real pilots flying real airplanes for about a hundred years.

That's why spin training isn't part of the PPL.