The rules on amending the soil have changed over the years.
Part of the change relates to the fact that good soil is hard to come by in newly developed subdivisions where enormous earth moving equipment is used to level trees and land.
This equipment not only removes the valuable topsoil, it also compacts subsoil and kills the living organisms that make up a healthy soil system.
The less we disturb the soil the better, but for many the reality is bleak that some sort of amendment is necessary in order to improve tilth, drainage and nutrition.