Who Tried Power Conditioners Over The Years and No Longer Use Them Today, Any Why?

Been thinking back to when I started in Audio and how good the system sounded with no power conditioners or fancy power cords. Then in the '90s slowly they both became a huge profit market for stores and manufacturers of them. If you used one on front end gear only or whole systems I will be interested in your real-world experience you could share with us all. I have a few so I am not against them, but I do at times have questions.