Not every carpet is created equally. If they were, your cleaning protocol would be easier to predict.
Various fibers and how they are used in carpet dictates how easy the carpet will be to clean, and how long it will last and retain its bulk, texture and color.
Professional carpet cleaners must know the fiber content of the carpet they clean. Fiber identification is a skill you can easily develop.
Of equal importance is knowing each fiber's characteristics. Each fiber has it's "pros and cons."
Your customers or clients often purchase carpet on impulse.