Well.. they HAD a purpose back in the day. In earlier, MUCH earlier versions of Android, task management was pretty bare bones. People would often have to go in and clear processes as they would run amok in the background, etc. But, and this has been the case for several major versions now, Android does quite well in handling processes both active and in the background. RAM management is much more robust (i.e. stop 'clearing all').
Of course, there are those out there that want to lay the hammer down. For those people? There are substantially better tools available, directed tools that WORK rather that dance about like a snake oil salesman, looking to get you to purchase a 'premium' all-in-one tool that serves nothing more than to puke ads at you.
Want to monitor battery usage better? Accubattery(
https://forums.androidcentral.com/e...rch?q=accubattery&c=apps&hl=en&token=tOW8eg7E) , GSAM(
https://forums.androidcentral.com/e...ails?id=com.gsamlabs.bbm&hl=en&token=sXsg5fNc) , Battey Monitor Widget(
https://forums.androidcentral.com/e...pps/details?id=ccc71.bmw&hl=en&token=WbVluAQO), Wakelock Detector (
https://forums.androidcentral.com/e....wakelockdetector.noroot&hl=en&token=PQGd0MYa) They'll give you more than you'd want to know... not all require root to function.
Want to be a little bit more strict on how apps behave in the background? Use Greenify. Want to go all scorched earth and have root access? Use a tool like Naptime (
https://forums.androidcentral.com/e...tails?id=com.franco.doze&hl=en&token=dP4VgD4R) and rule with an iron fist.
Storage usage is another sore spot. People tend to hoard digital bits on their phones, apps and files that they (or their apps) downloaded that they've more or less forgotten about. There are tools built into the operating system that can handle that. The Play Store can now sort apps based on how long its been since you've used them. And for all the crud left over in the internal storage, you can see high-level summaries in the Storage tools in Android settings, or you can use an app like DiskUsage (
https://forums.androidcentral.com/e...google.android.diskusage&hl=en&token=O6I93YXD) is vastly more useful than anything you get in a cleaner app.