Pot Power calculations is a searching process to determine the peak power (75- 99 % of linear pot). Why is this not normally discussed?
It's not normally that much of a consideration. Many pots are used as potentiometers (as opposed to rheostats) with negligible wiper current and/or used way, way below their rated dissipation as trimmers.
The pot dissipation rating is for the entire element, and any situation that exposes part of the element to a large proportion of the dissipation the entire element is rated for would best be derated considerably (and attention paid to any wiper current rating the manufacturer cares to share).
It does make a nice homework problem because it allows the student to apply simple calculus but has little practical value.
The greatest power dissipation per unit length of the element occurs as the wiper nears terminal 1. The greatest spot temperature rise on the element occurs with the wiper also near the maximum, depending on pot construction. It is the concentration of power dissipation that can cause unexpected damage. Ref. Potentiometer Handbook ISBN 0-07-006690-6