I have CCleaner on my Android, and I use Greenify to turn off apps that I am not using.
Somehow, CCleaner always turns itself back on, and is running in the background.
I see no good reason for a cleaner app to need to be constantly running.
Also, the app works flawlessly when I am on or offline, but malfunctions when my firewall is on if the web access for CCleaner is denied.
I use CCleaner because it works, but it is strange that the app wants to run all the time and will not function when my firewall is on.