Negative energy attracts bad spirits, so by removing that energy, we clean away the bad spirits that can interfere with your ritual.
Ideally, you don’t want to perform a cleansing unless you have the ability to see spirits…
…otherwise it would be like using a surgery knife without looking at the body, and with no practice beforehand.
Each spellcaster has different abilities, and those who aren’t able to see the spirits can do more harm than good.
Only those of us who can see spirits can make sure they are actually gone.
Same goes in a cleansing negative energy, you can’t clean things without looking at them… you might do something worse and create more negative energy and unwanted spirits.
With my safe cleansing of negative energy, you can be sure the negative energy and spirits will be gone, so that your ritual will be powerful and effective.